* * * * *



PRINTING LANTERN PICTURES BY ARTIFICIAL LIGHT ON BROMIDE PLATES FROM VARIOUS SIZES.

By A. PUMPHREY.

[Footnote: Read before the Birmingham Photographic Society. Reported in the Photo. News.]

There can be no question that there is no plan that is so simple for producing transparencies as contact printing, but in this, as in other photographic matters, one method of work will not answer all needs. Reproduction in the camera, using daylight to illuminate the negative, enables the operator to reduce or enlarge in every direction, but the lantern is a winter instrument, and comes in for demand and use during the short days. When even the professional photographer has not enough light to get through his orders, how can the amateur get the needed daylight if photography be only the pursuit in spare time? Besides, there are days in our large towns when what daylight there is is so yellow from smoke or fog as to have little actinic power. These considerations and needs have led me to experiment and test what can be done with artificial light, and I think I have made the way clear for actual work without further experiment. I have not been able by any arrangement of reflected light to get power enough to print negatives of the ordinary density, and have only succeeded by causing the light to be equally dispersed over the negative by a lens as used in the optical lantern, but the arrangements required are somewhat different to that of the enlarging lantern.

The following is the plan by which I have succeeded best in the production of transparencies:



B is a lamp with a circular wick, which burns petroleum and gives a good body of light.

C is a frame for holding the negative, on the opposite side of which is a double convex lens facing the light.

D is the camera and lens.

All these must be placed in a line, so that the best part of the light, the center of the condenser, and the lens are of equal height.

The method of working is as follows: The lamp, B, is placed at such a distance from the condenser that the rays come to a focus and enter the lens; the negative is then placed in the frame, the focus obtained, and the size of reduction adjusted by moving the camera nearer to or further from the condenser and negative. In doing this no attention need be paid to the light properly covering the field, as that cannot be adjusted while the negative is in its place. When the size and focus are obtained, remove the negative, and carefully move the lamp till it illuminates the ground glass equally all over, by a disk of light free from color.

The negative can then be replaced, and no further adjustment will be needed for any further reproduction of the same size.

There is one point that requires attention: The lens used in the camera should be a doublet of about 6 inch focus (in reproducing 81/2 x 61/2 or smaller sizes), and the stop used must not be a very small one, not less than 1/2 inch diameter. If a smaller stop is used, an even disk of light is not obtained, but ample definition is obtainable with the size stop mentioned.

In the arrangement described, a single lens is used for the condenser, not because it is better than a double one, as is general for such purposes, but because it is quite sufficient for the purpose. Of course, a large condenser is both expensive and cumbersome. There is, therefore, no advantage in using a combination if a single lens will answer.

In reproducing lantern pictures from half-plate negatives, the time required on my lantern plates is from two to four minutes, using 6 inch condenser. For whole plate negatives, from two to six minutes with a 9 inch condenser. In working in this way it is easy to be developing one picture while exposing another.

The condenser must be of such a size that it will cover the plate from corner to corner. The best part of an 81/2 x 61/2 negative will be covered by a 9 inch condenser, and a 61/2 x 43/4 by a 6 inch condenser.

With this arrangement it will be easy to reproduce from half or whole plate negatives or any intermediate sizes quite independently of daylight.

* * * * *



EXPERIMENTS IN TONING GELATINO-CHLORIDE PAPER.

From the Photographic News we take the following: The use of paper coated with a gelatino-citro-chloride emulsion in place of albumenized paper appears to be becoming daily more common. Successful toning has generally been the difficulty with such paper, the alkaline baths commonly in use with albumenized having proved unsuitable for toning this paper. On the whole, the bath that has given the best results is one containing, in addition to gold, a small quantity of hypo and a considerable quantity of sulphocyanide of ammonium. Such a bath tones very rapidly, and gives most pleasing colors. It appears, moreover, to be impossible to overtone the citro-chloro emulsion paper with it in the sense that it is possible to overtone prints on albumenized paper with the ordinary alkaline bath. That is to say, it is impossible to produce a slaty gray image. The result of prolonged toning is merely an image of an engraving black color. Of this, however, we shall say more hereafter. We wish first of all to refer to an elaborate series of experiments by Lionel Clark on the effects of various toning baths used with the gelatino-citro-chloride paper.

The results of these experiments we have before us at the time of writing, and we may at once say that, from the manner in which the experiments have been carried out and in which the results have been tabulated, Lionel Clark's work forms a very useful contribution to our photographic knowledge, and a contribution that will become more and more useful, the longer the results of the experiments are kept. A number of small prints have been prepared. Of these several—in most cases, three—have been toned by a certain bath, and each print has been torn in two. One-half has been treated with bichloride of mercury, so as to bleach such portion of the image as is of silver, and finally the prints—the two halves of each being brought close together—have been mounted in groups, each group containing all the prints toned by a certain formula, with full information tabulated.

The only improvement we could suggest in the arrangement is that all the prints should have been from the same negative, or from only three negatives, so that we should have prints from the same negatives in every group, and should the better be able to compare the results of the toning baths. Probably, however, the indifferent light of the present season of the year made it difficult to get a sufficiency of prints from one negative.

The following is a description of the toning baths used and of the appearance of the prints. We refer, in the mean time, only to those halves that have not been treated with bichloride of mercury.

1.—Gold chloride (AuCl_{3})........... 1 gr. Sulphocyanide of potassium......... 10 gr. Hyposulphite of soda............... 1/2 gr. Water.............................. 2 oz.

The prints are of a brilliant purple or violet color.

2.—Gold chloride...................... 1 gr. Sulphocyanide of potassium......... 10 gr. Hyposulphite of soda............... 1/2 gr. Water.............................. 4 oz.

There is only one print, which is of a brown color, and in every way inferior to those toned with the first bath.

3.—Gold chloride...................... 1 gr. Sulphocyanide of potassium......... 12 gr. Hyposulphite of soda............... 1/2 gr. Water.............................. 2 oz.

The prints toned by this bath are, in our opinion, the finest of the whole. The tone is a purple of the most brilliant and pleasing shade.

4.—Gold chloride...................... 1 gr. Sulphocyanide of potassium......... 20 gr. Hyposulphite of soda............... 5 gr. Water.............................. 2 oz.

There is only one print, but it is from the same negative as one of the No. 3 group. It is very inferior to that in No. 3, the color less pleasant, and the appearance generally as if the details of the lights had been bleached by the large quantity either of hypo or of sulphocyanide of potassium.

5.—Gold chloride...................... 1 gr. Sulphocyanide of potassium......... 50 gr. Hyposulphite of soda............... 1/2 gr. Water.............................. 2 oz.

Opposite to this description of formula there are no prints, but the following is written: "These prints were completely destroyed, the sulphocyanide of potassium (probably) dissolving off the gelatine."

6.—Gold chloride...................... 1 gr. Sulphocyanide of potassium......... 20 gr. Hypo............................... 5 gr. Carbonate of soda.................. 10 gr. Water.............................. 2 oz.

This it will be seen is the same as 4, but that the solution is rendered alkaline with carbonate of soda. The result of the alkalinity certainly appears to be good, the color is more pleasing than that produced by No. 4, and there is less appearance of bleaching. It must be borne in mind in this connection that the paper itself is strongly acid, and that, unless special means be taken to prevent it, the toning bath is sure to be more or less acid.

7.—Gold chloride...................... 1 gr. Acetate of soda.................... 30 gr. Water.............................. 2 oz.

The color of the prints toned by this bath is not exceedingly pleasing. It is a brown tending to purple, but is not very pure or bright. The results show, however, the possibility of toning the gelatino-chloro-citrate paper with the ordinary acetate bath if it be only made concentrated enough.

8.—Gold chloride...................... 1 gr. Carbonate of soda.................. 3 gr. Water.............................. 2 oz.

Very much the same may be said of the prints toned by this bath as of those toned by No. 7. The color is not very good, nor is the toning quite even. This last remark applies to No. 7 batch as well as No. 8.

9.—Gold chloride...................... 1 gr. Phosphate of soda.................. 20 gr. Water.............................. 2 oz.

The results of this bath can best be described as purplish in color. They are decidedly more pleasing than those of 7 or 8, but are not as good as the best by the sulphocyanide bath.

10.—Gold chloride..................... 1 gr. Hyposulphite of soda.............. 1/2 oz. Water............................. 2 oz.

The result of this bath is a brilliant brown color, what might indeed, perhaps, be best described as a red. Two out of the three prints are much too dark, indicating, perhaps, that this toning bath did not have any tendency to reduce the intensity of the image.

The general lesson taught by Clark's experiments is that the sulphocyanide bath gives better results than any other. A certain proportion of the ingredients—namely, that of bath No. 3—gives better results than any other proportions tried, and about as good as any that could be hoped for. Any of the ordinary alkaline toning baths may be used, but they all give results inferior to those got by the sulphocyanide bath. The best of the ordinary baths is, however, the phosphate of soda.

And now a word as to those parts of the prints which have been treated with bichloride of mercury. The thing that strikes us as remarkable in connection with them is that in them the image has scarcely suffered any reduction of intensity at all. In most cases there has been a disagreeable change of color, but it is almost entirely confined to the whites and lighter tints, which are turned to a more or less dirty yellow. Even in the case of the prints toned by bath No. 10, where the image is quite red, it has suffered no appreciable reduction of intensity.

This would indicate that an unusually large proportion of the toned image consists of gold, and this idea is confirmed by the fact that to tone a sheet of gelatino-chloro-citrate paper requires several times as much gold as to tone a sheet of albumenized paper. Indeed, we believe that, with the emulsion paper, it is possible to replace the whole of the silver of the image with gold, thereby producing a permanent print. We have already said that the print may be left for any reasonable length of time in the toning bath without the destruction of its appearance, and we cannot but suppose that a very long immersion results in a complete substitution of gold for silver.

* * * * *



THE "SENSIM" PREPARING BOX.

Fig. 1 shows a perspective view of the machine, Fig. 2 a sectional elevation, and Fig. 3 a plan. In the ordinary screw gill box, the screws which traverse the gills are uniform in their pitch, so that a draught is only obtained between the feed rollers and the first gill, between the last gill of the first set and the first of the second, and between the last gill of the second set and the delivery roller. As thus arranged, the gills are really not active workers after their first draw during the remainder of their traverse, but simply carriers of the wool to the next set. It is somewhat remarkable, as may indeed be said of every invention, that this fact has only been just observed, and suggested an improvement. There is no reason why each gill should not be continuously working to the end of the traverse, and only cease during its return to its first position. The perception of this has led to several attempts to realize this improvement. The inventor in the present case seems to have solved the problem in a very perfect manner by the introduction of gill screws of a gradually increasing pitch, by which the progress of the gills, B, through the box is constantly undergoing acceleration to the end, as will be obvious from the construction of the screws, A and A, until they are passed down in the usual manner, and returned by the screws, C and C, which are, as usual, of uniform pitch. The two sets of screws are so adjusted as to almost meet in the middle, so that the gills of the first set finish their forward movement close to the point where the second commence. The bottom screws, C, of the first set of gills, B, are actuated by bevel wheels on a cross shaft engaging with bevel wheels on their outer extremity, the cross shaft being geared to the main shaft. The screws, C, of the second set of gills from two longitudinal shafts are connected by bevel gearing to the main shaft. Intermediate wheels communicate motion from change wheels on the longitudinal shafts to the wheels on the screw, C, traversing the second set of gills.



The feed and delivery rollers, D and E, are operated by gearing connected to worms on longitudinal shafts. These worms engage with worm wheels on cross shafts, which are provided at their outer ends with change wheels engaging with other change wheels on the arbors of the bottom feed and delivery rollers, D and E.



The speeds are so adjusted that the fibers are delivered to the first set of gills at a speed approximately equal to the speed at which these start their traverse. The gills in the second set begin their journey at a pace which slightly exceeds that at which those of the first finish their traverse. These paces are of course regulated by the class and nature of the fibers under operation. The delivery rollers, E, take off the fibers at a rate slightly exceeding that of the gills delivering it to them.



In the ordinary gill box, the feed and delivery rollers are fluted, in order the better to retain in the first instance their grip upon the wool passing through, and in the second to enable them to overcome any resistance that might be offered to drawing the material. It thus often happens in this class of machines that a large percentage of the fibers are broken, and thus much waste is made. The substitution of plain rollers in both these positions obviates most of this mischief, while in combination with the other parts of the arrangement it is almost precluded altogether.

It will be obvious from what we have said that the special features of this machine, which may be summarized as, first, the use of a screw thread of graduated pitch; second, an increased length of screw action and an additional number of fallers; and third, the use of light plain rollers in place of heavy fluted back and front rollers, enable the inventor to justly claim the acquisition of a number of advantages, which may be enumerated as follows:

The transformation of the gills from mere carriers into constant workers during the whole of their outward traverse, by which the work is done much more efficiently, more gently, and in greater quantity than by the old system with uniformly pitched screws. A great improvement in the quality of the work, resulting from the breakage of fiber being, if not entirely obviated, nearly. An increased yield and better quality of top, owing to the absence of broken fiber, and consequent diminution of noil and waste. The better working of cotted wools, which can be brought to a proper condition with far more facility and with diminished risk of breaking pins than before. A saving in labor, space, and plant also results from the fact that the wool is as well opened and straightened for carding with a passage through a pair of improved boxes as it is in going through four of the ordinary ones, while the quantity will be as great. Owing to the first feature referred to, which distributes the strain over all the gills, a greater weight of wool can be put into them and a higher speed be worked. The space occupied and the attendance required is only about half that of boxes required to do the same amount of work on the old system. Taking the flutes out of the feed and delivery rollers, and greatly diminishing their weight, it is estimated will reduce by 90 per cent. the wear and tear of the leather aprons, and thus to that extent diminish a very heavy annual outlay incident to the system generally in vogue. A considerable saving of power for driving and of time and cost of repairs from the bending and breakage of pins also results. Shaw, Harrison & Co., makers, Bradford.—Textile Manufacturer.

* * * * *



NOTES ON GARMENT DYEING.

Black wool dresses for renewing and checked goods, with the check not covered by the first operation, are operated upon as follows:

Preparation or mordant for eight black dresses for renewing the color.

2 oz. Chrome. 2 " Argol or Tartar.

Or without argol or tartar, but I think their use is beneficial. Boil twenty minutes, lift, rinse through two waters.

To prepare dye boiler, put in 2 lb. logwood, boil twenty minutes. Clear the face same way as before described. Those with cotton and made-up dresses sewn with cotton same operation as before mentioned, using half the quantity of stuffs, and working cold throughout. Since the introduction of aniline black, some dyers use it in place of logwood both for wool and cotton. It answers very well for dippers, substituting 2 oz. aniline black for every pound logwood required. In dyeing light bottoms it is more expensive than logwood, even though the liquor be kept up, and, in my opinion, not so clear and black.

Silk and wool dresses, poplins, and woolen dresses trimmed with silk, etc., for black.—Before the dyeing operations, steep the goods in hand-heat soda water, rinse through two warm waters. Discharge blues, mauves, etc., with diluted aquafortis (nitric acid). A skilled dyer can perform this operation without the least injury to the goods. This liquor is kept in stoneware, or a vessel made of caoutchouc composition, or a large stone hollowed out of five slabs of stone, forming the bottom and four sides, braced together, and luted with caoutchouc, forming a water-tight vessel. The latter is the most convenient vessel, as it can be repaired. The others when once rent are past repair. The steam is introduced by means of a caoutchouc pipe, and when brought to the boil the pipe is removed. After the colors are discharged, rinse through three warm waters. They are then ready to receive the mordant and the dye.

Note.—The aquafortis vessel to be outside the dye-house, or, if inside, to be provided with a funnel to carry away the nitrous fumes, as it is dangerous to other colors.

Preparation or mordant for eight dresses, silk and wool mixed, for black.

4 lb. Copperas. 1/2 " Bluestone. 1/2 " Tartar.

Bring to the boil, dissolve the copperas, etc., shut off steam, enter the goods, handle gently (or else they will be faced, i.e., look gray on face when dyed) for one hour, lift, air, rinse through three warm waters.

To prepare dye boiler, bring to boil, put in 8 lb. logwood (previously boiled), 1 lb. black or brown oil soap, shut off steam, enter goods, gently handle for half an hour, add another pound of soap (have the soap dissolved ready), and keep moving for another half hour, lift, finish in hand-heat soap. If very heavy, run through lukewarm water slightly acidulated with vitriol, rinse, hydro-extract, and hang in stove. Another method to clear them: Make up three lukewarm waters, in first put some bleaching liquor, in second a little vitriol, handle these two, and rinse through the third, hydro-extract, and hang in stove.

Note.—This is the method employed generally in small dye-works for all dresses for black; their lots are so small. This preparation can be kept up, if care is taken that none of the sediment of the copperas (oxide of iron) is introduced when charging, as the oxide of iron creates stains. This also happens when the water used contains iron in quantity or impure copperas. The remedy is to substitute half a gill of vitriol in place of tartar.

Silk, wool, and cotton mixed dresses, for black.—Dye the silk and wool as before described, and also the cotton in the manner previously mentioned.

Another method to dye the mixed silk and wool and cotton dresses black, four dresses.—Bring boiler to the boil, put in 3 or 4 oz. aniline black, either the deep black or the blue black or a mixture of the two, add 1/4 gill hydrochloric acid or sulphuric acid, or 3 oz. oxalic acid, shut off steam, enter, and handle for half an hour, lift, rinse through water, dye the cotton in the manner previously described.—Dyer.

* * * * *



FUEL AND SMOKE.

[Footnote: Second of two lectures delivered at the Royal Institution, London, on 17th April, 1886. Continued from SUPPLEMENT, No. 585, p. 9340.]

By Prof. OLIVER LODGE.

LECTURE II.

The points to which I specially called your attention in the first lecture, and which it is necessary to recapitulate to-day, are these: (1) That coal is distilled, or burned partly into gas, before it can be burned. (2) That the gas, so given off, if mixed with carbonic acid, cannot be expected to burn properly or completely. (3) That to burn the gas, a sufficient supply of air must be introduced at a temperature not low enough to cool the gases below their igniting point. (4) That in stoking a fire, a small amount should be added at a time because of the heat required to warm and distill the fresh coal. (5) That fresh coal should be put in front of or at the bottom of a fire, so that the gas may be thoroughly heated by the incandescent mass above and thus, if there be sufficient air, have a chance of burning. A fire may be inverted, so that the draught proceeds through it downward. This is the arrangement in several stoves, and in them, of course, fresh coal is put at the top.

Two simple principles are at the root of all fire management: (1) Coal gas must be at a certain temperature before it can burn; and (2) it must have a sufficient supply of air. Very simple, very obvious, but also extremely important, and frequently altogether ignored. In a common open fire they are both ignored. Coal is put on the top of a glowing mass of charcoal, and the gas distilled off is for a longtime much too cold for ignition, and when it does catch fire it is too mixed with carbonic acid to burn completely or steadily. In order to satisfy the first condition better, and keep the gases at a higher temperature, Dr. Pridgin Teale arranges a sloping fire-clay slab above his fire. On this the gases play, and its temperature helps them to ignite. It also acts as a radiator, and is said to be very efficient.

In a close stove and in many furnaces the second condition is violated; there is an insufficient supply of air; fresh coal is put on, and the feeding doors are shut. Gas is distilled off, but where is it to get any air from? How on earth can it be expected to burn? Whether it be expected or not, it certainly does not burn, and such a stove is nothing else than a gas works, making crude gas, and wasting it—it is a soot and smoke factory.

Most slow combustion stoves are apt to err in this way; you make the combustion slow by cutting off air, and you run the risk of stopping the combustion altogether. When you wish a stove to burn better, it is customary to open a trap door below the fuel; this makes the red hot mass glow more vigorously, but the oxygen will soon become CO_{2}, and be unable to burn the gas.

The right way to check the ardor of a stove is not to shut off the air supply and make it distill its gases unconsumed, but to admit so much air above the fire that the draught is checked by the chimney ceasing to draw so fiercely. You at the same time secure better ventilation; and if the fire becomes visible to the room so much the better and more cheerful. But if you open up the top of a stove like this, it becomes, to all intents and purposes, an open fire. Quite so, and in many respects, therefore, an open fire is an improvement on a close stove. An open fire has faults, and it certainly wastes heat up the chimney. A close stove may have more faults—it wastes less heat, but it is liable to waste gas up the chimney—not necessarily visible or smoky gas; it may waste it from coke or anthracite, as CO.

You now easily perceive the principles on which so-called smoke consumers are based. They are all special arrangements or appendages to a furnace for permitting complete combustion by satisfying the two conditions which had been violated in its original construction. But there is this difficulty about the air supply to a furnace: the needful amount is variable if the stoking be intermittent, and if you let in more than the needful amount, you are unnecessarily wasting heat and cooling the boiler, or whatever it is, by a draught of cold air.

Every time a fresh shovelful is thrown on, a great production of gas occurs, and if it is to flame it must have a correspondingly great supply of air. After a time, when the mass has become red hot, it can get nearly enough air through the bars. But at first the evolution of gas actually checks the draught. But remember that although no smoke is visible from a glowing mass, it by no means follows that its combustion is perfect. On an open fire it probably is perfect, but not necessarily in a close stove or furnace. If you diminish the supply of air much (as by clogging your furnace bars and keeping the doors shut), you will be merely distilling carbonic oxide up the chimney—a poisonous gas, of which probably a considerable quantity is frequently given off from close stoves.

Now let us look at some smoke consumers. The diagrams show those of Chubb, Growthorpe, Ireland and Lowndes, and of Gregory. You see that they all admit air at the "bridge" or back of the fire, and that this air is warmed either by passing under or round the furnace, or in one case through hollow fire bars. The regulation of the air supply is effected by hand, and it is clear that some of these arrangements are liable to admit an unnecessary supply of air, while others scarcely admit enough, especially when fresh coal is put on. This is the difficulty with all these arrangements when used with ordinary hand—i.e., intermittent—stoking. Two plans are open to us to overcome the difficulty. Either the stoking and the air supply must both be regular and continuous, or the air supply be made intermittent to suit the stoking. The first method is carried out in any of the many forms of mechanical stoker, of which this of Sinclair's is an admirable specimen. Fresh fuel is perpetually being pushed on in front, and by alternate movement of the fire bars the fire is kept in perpetual motion till the ashes drop out at the back. To such an arrangement as this a steady air supply can be adjusted, and if the boiler demand is constant there is no need for smoke, and an inferior fuel may be used. The other plan is to vary the air supply to suit the stoking. This is effected by Prideaux automatic furnace doors, which have louvers to remain open for a certain time after the doors are shut, and so to admit extra air immediately after coal has been put on, the supply gradually decreasing as distillation ceases. The worst of air admitted through chinks in the doors, or through partly open doors, is that it is admitted cold, and scarcely gets thoroughly warm before it is among the stuff it has to burn. Still this is not a fatal objection, though a hot blast would be better. Nothing can be worse than shoveling on a quantity of coal and shutting it up completely. Every condition of combustion is thus violated, and the intended furnace is a mere gas retort.

Gas Producers.—Suppose the conditions of combustion are purposely violated; we at once have a gas producer. That is all gas producers are, extra bad stoves or furnaces, not always much worse than things which pretend to serve for combustion. Consider how ordinary gas is made. There is a red-hot retort or cylinder plunged in a furnace. Into this tube you shovel a quantity of coal, which flames vigorously as long as the door is open, but when it is full you shut the door, thus cutting off the supply of air and extinguishing the flame. Gas is now simply distilled, and passes along pipes to be purified and stored. You perceive at once that the difference between a gas retort and an ordinary furnace with closed doors and half choked fire bars is not very great. Consumption of smoke! It is not smoke consumers you really want, it is fuel consumers. You distill your fuel instead of burning it, in fully one-half, might I not say nine-tenths, of existing furnaces and close stoves. But in an ordinary gas retort the heat required to distill the gas is furnished by an outside fire; this is only necessary when you require lighting gas, with no admixture of carbonic acid and as little carbonic oxide as possible. If you wish for heating gas, you need no outside fire; a small fire at the bottom of a mass of coal will serve to distill it, and you will have most of the carbon also converted into gas. Here, for instance, is Siemens' gas producer. The mass of coal is burning at the bottom, with a very limited supply of air. The carbonic acid formed rises over the glowing coke, and takes up another atom of carbon to form the combustible gas carbonic oxide. This and the hot nitrogen passing over and through the coal above distill away its volatile constituents, and the whole mass of gas leaves by the exit pipe. Some art is needed in adjusting the path of the gases distilled from the fresh coal with reference to the hot mass below. If they pass too readily, and at too low a temperature, to the exit pipe, this is apt to get choked with tar and dense hydrocarbons. If it is carried down near or through the hot fuel below, the hydrocarbons are decomposed over much, and the quality of the gas becomes poor. Moreover, it is not possible to make the gases pass freely through a mass of hot coke; it is apt to get clogged. The best plan is to make the hydrocarbon gas pass over and near a red-hot surface, so as to have its heaviest hydrocarbons decomposed, but so as to leave all those which are able to pass away as gas uninjured, for it is to the presence of these that the gas will owe its richness as a combustible material, especially when radiant heat is made use of.

The only inert and useless gas in an arrangement like this is the nitrogen of the air, which being in large quantities does act as a serious diluent. To diminish the proportion of nitrogen, steam is often injected as well as air. The glowing coke can decompose the steam, forming carbonic oxide and hydrogen, both combustible. But of course no extra energy can be gained by the use of steam in this way; all the energy must come from the coke, the steam being already a perfectly burned product; the use of steam is merely to serve as a vehicle for converting the carbon into a convenient gaseous equivalent. Moreover, steam injected into coke cannot keep up the combustion; it would soon put the fire out unless air is introduced too. Some air is necessary to keep up the combustion, and therefore some nitrogen is unavoidable. But some steam is advisable in every gas producer, unless pure oxygen could be used instead of air; or unless some substance like quicklime, which holds its oxygen with less vigor than carbon does, were mixed with the coke and used to maintain the heat necessary for distillation. A well known gas producer for small scale use is Dowson's. Steam is superheated in a coil of pipe, and blown through glowing anthracite along with air. The gas which comes off consists of 20 per cent. hydrogen, 30 per cent. carbonic oxide, 3 per cent. carbonic acid, and 47 per cent. nitrogen. It is a weak gas, but it serves for gas engines, and is used, I believe, by Thompson, of Leeds, for firing glass and pottery in a gas kiln. It is said to cost 4d. per 1,000 ft., and to be half as good as coal gas.

For furnace work, where gas is needed in large quantities, it must be made on the spot. And what I want to insist upon is this, that all well-regulated furnaces are gas retorts and combustion chambers combined. You may talk of burning coal, but you can't do it; you must distill it first, and you may either waste the gas so formed or you may burn it properly. The thing is to let in not too much air, but just air enough. Look, for instance, at Minton's oven for firing pottery. Round the central chamber are the coal hoppers, and from each of these gas is distilled, passes into the central chamber, where the ware is stacked, and meeting with an adjusted supply of air as it rises, it burns in a large flame, which extends through the whole space and swathes the material to be heated. It makes its exit by a central hole in the floor, and thence rises by flues to a common opening above. When these ovens are in thorough action, nothing visible escapes. The smoke from ordinary potters' ovens is in Staffordshire a familiar nuisance. In the Siemens gas producer and furnace, of which Mr. Frederick Siemens has been good enough to lend me this diagram, the gas is not made so closely on the spot, the gas retort and furnace being separated by a hundred yards or so in order to give the required propelling force. But the principle is the same; the coal is first distilled, then burnt. But to get high temperature, the air supply to the furnace must be heated, and there must be no excess. If this is carried on by means of otherwise waste heat we have the regenerative principle, so admirably applied by the Brothers Siemens, where the waste heat of the products of combustion is used to heat the incoming air and gas supply. The reversing arrangement by which the temperature of such a furnace can be gradually worked up from ordinary flame temperature to something near the dissociation point of gases, far above the melting point of steel, is well known, and has already been described in this place. Mr. Siemens has lent me this beautiful model of the most recent form of his furnace, showing its application to steel making and to glass working.

The most remarkable and, at first sight, astounding thing about this furnace is, however, that it works solely by radiation. The flames do not touch the material to be heated; they burn above it, and radiate their heat down to it. This I regard as one of the most important discoveries in the whole subject, viz., that to get the highest temperature and greatest economy out of the combustion of coal, one must work directly by radiant heat only, all other heat being utilized indirectly to warm the air and gas supply, and thus to raise the flame to an intensely high temperature.

It is easy to show the effect of supplying a common gas flame with warm air by holding it over a cylinder packed with wire gauze which has been made red hot. A common burner held over such a hot air shaft burns far more brightly and whitely. There is no question but that this is the plan to get good illumination out of gas combustion; and many regenerative burners are now in the market, all depending on this principle, and utilizing the waste heat to make a high temperature flame. But although it is evidently the right way to get light, it was by no means evidently the right way to get heat. Yet so it turns out, not by warming solid objects or by dull warm surfaces, but by the brilliant radiation of the hottest flame that can be procured, will rooms be warmed in the future. And if one wants to boil a kettle, it will be done, not by putting it into a non-luminous flame, and so interfering with the combustion, but by holding it near to a freely burning regenerated flame, and using the radiation only. Making toast is the symbol of all the heating of the future, provided we regard Mr. Siemens' view as well established.

The ideas are founded on something like the following considerations: Flame cannot touch a cold surface, i.e., one below the temperature of combustion, because by the contact it would be put out. Hence, between a flame and the surface to be heated by it there always intervenes a comparatively cool space, across which heat must pass by radiation. It is by radiation ultimately, therefore, that all bodies get heated. This being so, it is well to increase the radiating power of flame as much as possible. Now, radiating power depends on two things: the presence of solid matter in the flame in a fine state of subdivision, and the temperature to which it is heated. Solid matter is most easily provided by burning a gas rich in dense hydrocarbons, not a poor and non-luminous gas. To mix the gas with air so as to destroy and burn up these hydrocarbons seems therefore to be a retrograde step, useful undoubtedly in certain cases, as in the Bunsen flame of the laboratory, but not the ideal method of combustion. The ideal method looks to the use of a very rich gas, and the burning of it with a maximum of luminosity. The hot products of combustion must give up their heat by contact. It is for them that cross tubes in boilers are useful. They have no combustion to be interfered with by cold contacts. The flame only should be free.

The second condition of radiation was high temperature. What limits the temperature of a flame? Dissociation or splitting up of a compound by heat. So soon as the temperature reaches the dissociation point at which the compound can no longer exist, combustion ceases. Anything short of this may theoretically be obtained.

But Mr. Siemens believes, and adduces some evidence to prove, that the dissociation point is not a constant and definite temperature for a given compound; it depends entirely upon whether solid or foreign surfaces are present or not. These it is which appear to be an efficient cause of dissociation, and which, therefore, limit the temperature of flame. In the absence of all solid contact, Mr. Siemens believes that dissociation, if it occur at all, occurs at an enormously higher temperature, and that the temperature of free flame can be raised to almost any extent. Whether this be so or not, his radiating flames are most successful, and the fact that large quantities of steel are now melted by mere flame radiation speaks well for the correctness of the theory upon which his practice has been based.

Use of Small Coal.—Meanwhile, we may just consider how we ought to deal with solid fuel, whether for the purpose of making gas from it or for burning it in situ. The question arises, In what form ought solid fuel to be—ought it to be in lumps or in powder? Universal practice says lumps, but some theoretical considerations would have suggested powder. Remember, combustion is a chemical action, and when a chemist wishes to act on a solid easily, he always pulverizes it as a first step.

Is it not possible that compacting small coal into lumps is a wrong operation, and that we ought rather to think of breaking big coal down into slack? The idea was suggested to me by Sir W. Thomson in a chance conversation, and it struck me at once as a brilliant one. The amount of coal wasted by being in the form of slack is very great. Thousands of tons are never raised from the pits because the price is too low to pay for the raising—in some places it is only 1s. 6d. a ton. Mr. McMillan calculates that 130,000 tons of breeze, or powdered coke, is produced every year by the Gas Light and Coke Company alone, and its price is 3s. a ton at the works, or 5s. delivered.

The low price and refuse character of small coal is, of course, owing to the fact that no ordinary furnace can burn it. But picture to yourself a blast of hot air into which powdered coal is sifted from above like ground coffee, or like chaff in a thrashing mill, and see how rapidly and completely it might burn. Fine dust in a flour mill is so combustible as to be explosive and dangerous, and Mr. Galloway has shown that many colliery explosions are due not to the presence of gas so much as the presence of fine coal-dust suspended in the air. If only fine enough, then such dust is eminently combustible, and a blast containing it might become a veritable sheet of flame. (Blow lycopodium through a flame.) Feed the coal into a sort of coffee-mill, there let it be ground and carried forward by a blast to the furnace where it is to be burned. If the thing would work at all, almost any kind of refuse fuel could be burned—sawdust, tan, cinder heaps, organic rubbish of all kinds. The only condition is that it be fine enough.

Attempts in this direction have been made by Mr. T.R. Crampton, by Messrs. Whelpley and Storer, and by Mr. G.K. Stephenson; but a difficulty has presented itself which seems at present to be insuperable, that the slag fluxes the walls of the furnace, and at that high temperature destroys them. If it be feasible to keep the flame out of contact with solid surfaces, however, perhaps even this difficulty can be overcome.

Some success in blast burning of dust fuel has been attained in the more commonplace method of the blacksmith's forge, and a boiler furnace is arranged at Messrs. Donkin's works at Bermondsey on this principle. A pressure of about half an inch of water is produced by a fan and used to drive air through the bars into a chimney draw of another half-inch. The fire bars are protected from the high temperatures by having blades which dip into water, and so keep fairly cool. A totally different method of burning dust fuel by smouldering is attained in M. Ferret's low temperature furnace by exposing the fuel in a series of broad, shallow trays to a gentle draught of air. The fuel is fed into the top of such a furnace, and either by raking or by shaking it descends occasionally, stage by stage, till it arrives at the bottom, where it is utterly inorganic and mere refuse. A beautiful earthworm economy of the last dregs of combustible matter in any kind of refuse can thus be attained. Such methods of combustion as this, though valuable, are plainly of limited application; but for the great bulk of fuel consumption some gas-making process must be looked to. No crude combustion of solid fuel can give ultimate perfection.

Coal tar products, though not so expensive as they were some time back, are still too valuable entirely to waste, and the importance of exceedingly cheap and fertilizing manure in the reclamation of waste lands and the improvement of soil is a question likely to become of most supreme importance in this overcrowded island. Indeed, if we are to believe the social philosophers, the naturally fertile lands of the earth may before long become insufficient for the needs of the human race; and posterity may then be largely dependent for their daily bread upon the fertilizing essences of the stored-up plants of the carboniferous epoch, just as we are largely dependent on the stored-up sunlight of that period for our light, our warmth, and our power. They will not then burn crude coal, therefore. They will carefully distill it—extract its valuable juices—and will supply for combustion only its carbureted hydrogen and its carbon in some gaseous or finely divided form.

Gaseous fuel is more manageable in every way than solid fuel, and is far more easily and reliably conveyed from place to place. Dr. Siemens, you remember, expected that coal would not even be raised, but turned into gas in the pits, to rise by its own buoyancy to be burnt on the surface wherever wanted. And not only will the useful products be first removed and saved, its sulphur will be removed too; not because it is valuable, but because its product of combustion is a poisonous nuisance. Depend upon it, the cities of the future will not allow people to turn sulphurous acid wholesale into the air, there to oxidize and become oil of vitriol. Even if it entails a slight strain upon the purse they will, I hope, be wise enough to prefer it to the more serious strain upon their lungs. We forbid sulphur as much as possible in our lighting gas, because we find it is deleterious in our rooms. But what is London but one huge room packed with over four millions of inhabitants? The air of a city is limited, fearfully limited, and we allow all this horrible stuff to be belched out of hundreds of thousands of chimneys all day long.

Get up and see London at four or five in the morning, and compare it with four or five in the afternoon; the contrast is painful. A city might be delightful, but you make it loathsome; not only by smoke, indeed, but still greatly by smoke. When no one is about, then the air is almost pure; have it well fouled before you rise to enjoy it. Where no one lives, the breeze of heaven still blows; where human life is thickest, there it is not fit to live. Is it not an anomaly, is it not farcical? What term is strong enough to stigmatize such suicidal folly? But we will not be in earnest, and our rulers will talk, and our lives will go on and go out, and next century will be soon upon us, and here is a reform gigantic, ready to our hands, easy to accomplish, really easy to accomplish if the right heads and vigorous means were devoted to it. Surely something will be done.

The following references may be found useful in seeking for more detailed information: Report of the Smoke Abatement Committee for 1882, by Chandler Roberts and D.K. Clark. "How to Use Gas," by F.T. Bond; Sanitary Association, Gloucester. "Recovery of Volatile Constituents of Coal," by T.B. Lightfoot; Journal Society of Arts, May, 1883. "Manufacture of Gas from Oil," by H.E. Armstrong; Journal Society of Chemical Industry, September, 1884. "Coking Coal," by H.E. Armstrong; Iron and Steel Institute, 1885. "Modified Siemens Producer," by John Head; Iron and Steel Institute, 1885. "Utilization of Dust Fuel," by W.G. McMillan; Journal Society of Arts, April. 1886. "Gas Producers," by Rowan; Proc. Inst. C.E., January, 1886. "Regenerative Furnaces with Radiation," and "On Producers," by F. Siemens; Journal Soc. Chem. Industry, July, 1885, and November, 1885. "Fireplace Construction," by Pridgin Teale; the Builder, February, 1886. "On Dissociation Temperatures," by Frederick Siemens; Royal Institution, May 7, 1886.

* * * * *

Near Colorados, in the Argentine Republic, a large bed of superior coal has been opened, and to the west of the Province of Buenos Ayres extensive borax deposits have been discovered.

* * * * *



THE ANTI-FRICTION CONVEYER.

The accompanying engraving illustrates a remarkable invention. For ages, screw conveyers for corn and meal have been employed, and in spite of the power consumed and the rubbing of the material conveyed, they have remained, with little exception, unimproved and without a rival. Now we have a new conveyer, which, says The Engineer, in its simplicity excels anything brought out for many years, and, until it is seen at work, makes a heavier demand upon one's credulity than is often made by new mechanical inventions. As will be seen from the engravings, the new conveyer consists simply of a spiral of round steel rod mounted upon a quickly revolving spindle by means of suitable clamps and arms. The spiral as made for England is of 5/8 in. steel rod, because English people would not be inclined to try what is really sufficient in most cases, namely, a mere wire. The working of this spiral as a conveyer is simply magical. A 6 in. spiral delivers 800 bushels per hour at 100 revolutions per minute, and more in proportion at higher speeds. A little 4 in. spiral delivers 200 bushels per hour at 100 revolutions per minute. It seems to act as a mere persuader. The spiral moves a small quantity, and sets the whole contents of the trough in motion. In fact, it embodies the great essentials of success, namely, simplicity, great capacity for work, and cheapness. It is the invention of Mr. J. Little, and is made by the Anti-friction Conveyer Company, of 59 Mark Lane, London.



Since the days of Archimedes, who is credited with being the inventor of the screw, there has not been any improvement in the principle of the worm conveyer. There have been several patents taken out for improved methods of manufacturing the old-fashioned continuous and paddle-blade worms, but Mr. Little's patent is the first for an entirely new kind of conveyer.

* * * * *



STUDIES IN PYROTECHNY.

[Footnote: Continued from SUPPLEMENT, No. 583, page 9303.]

II. METHODS OF ILLUMINATION.

Torches consist of a bundle of loosely twisted threads which has been immersed in a mixture formed of two parts, by weight, of beeswax, eight of resin, and one of tallow. In warm, dry weather, these torches when lighted last for two hours when at rest, and for an hour and a quarter on a march. A good light is obtained by spacing them 20 or 30 yards apart.

Another style of torch consists of a cardboard cylinder fitted with a composition consisting of 100 parts of saltpeter, 60 of sulphur, 8 of priming powder, and 30 of pulverized glass, the whole sifted and well mixed. This torch, which burns for a quarter of an hour, illuminates a space within a radius of 180 or 200 yards very well.

The tourteau goudronne (lit. "tarred coke") is merely a ring formed of old lunt or of cords well beaten with a mallet (Fig. 10). This ring is first impregnated with a composition formed of 20 parts of black pitch and 1 of tallow, and then with another one formed of equal parts of black pitch and resin. One of these torches will burn for an hour in calm weather, and half an hour in the wind. Rain does not affect the burning of it. These rings are usually arranged in pairs on brackets with two branches and an upper circle, the whole of iron, and these brackets are spaced a hundred yards apart.



A tarred fascine consists of a small fagot of dry wood, 20 inches in length by 4 in diameter, covered with the same composition as the preceding (Fig. 11). Fascines thus prepared burn for about half an hour. They are placed upright in supports, and these latter are located at intervals of twenty yards.

The Lamarre compositions are all formed of a combustible substance, such as boiled oil,[1] of a substance that burns, such as chlorate of potash, and of various coloring salts.

[Footnote 1: For preparation see page 9304 of SUPPLEMENT.]

The white composition used for charging fire balls and 11/2 inch flambeaux is formed of 500 parts of powdered chlorate of potash, 1,500 of nitrate of baryta, 120 of light wood charcoal, and 250 of boiled oil. Another white composition, used for charging 3/4 inch flambeaux, consists of 1,000 parts of chlorate of potash, 1,000 of nitrate of baryta, and 175 of boiled oil.

The red composition used for making red flambeaux and percussion signals consists of 1,800 parts of chlorate of potash, 300 of oxalate of strontia, 300 of carbonate of strontia, 48 of whitewood charcoal, 240 of boiled oil, 6 of oil, and 14 of gum lac.

A red or white Lamarre flambeau consists of a sheet rubber tube filled with one of the above-named compositions. The lower extremity of this tube is closed with a cork. When the charging has been effected, the flambeau is primed by inserting a quickmatch in the composition. This is simply lighted with a match or a live coal. The composition of the Lamarre quickmatch will be given hereafter.

A Lamarre flambeau 11/2 inch in diameter and 3 inches in length will burn for about thirty-five minutes. One of the same length, and 3/4 inch in diameter, lasts but a quarter of an hour.

A fire ball consists of an open work sack internally strengthened with a sheet iron shell, and fitted with the Lamarre white composition. After the charging has been done, the sphere is wound with string, which is made to adhere by means of tar, and canvas is then wrapped around the whole. Projectiles of this kind, which have diameters of 6, 8, 11, and 13 inches, are shot from mortars.

The illuminating grenade (Fig. 13) consists of a sphere of vulcanized rubber, two inches in diameter, charged with the Lamarre white composition. The sphere contains an aperture to allow of the insertion of a fuse. The priming is effected by means of a tin tube filled with a composition consisting of three parts of priming powder, two of sulphur, and one of saltpeter. These grenades are thrown either by hand or with a sling, and they may likewise be shot from mortars. Each of these projectiles illuminates a circle thirty feet in diameter for a space of time that varies, according to the wind, from sixty to eighty seconds.

The percussion signal (Fig. 14) consists of a cylinder of zinc, one inch in diameter and one and a quarter inch in length, filled with Lamarre red composition. It is provided with a wooden handle, and the fuse consists of a capsule which is exploded by striking it against some rough object. This signal burns for nearly a minute.

Belgian illuminating balls and cylinders are canvas bags filled with certain compositions. The cylinders, five inches in diameter and seven in length, are charged with a mixture of six parts of sulphur, two of priming powder, one of antimony, and two of beeswax cut up into thin slices. They are primed with a quickmatch. The balls, one and a half inch in diameter, are charged with a composition consisting of twelve parts of saltpeter, eight of sulphur, four of priming powder, two of sawdust, two of beeswax, and two of tallow. They are thrown by hand. They burn for six minutes.

Illuminating kegs (Fig. 15) consist of powder kegs filled with shavings covered with pitch. An aperture two or three inches in diameter is made in each head, and then a large number of holes, half an inch in diameter, and arranged quincuncially, are bored in the staves and heads. All these apertures are filled with port-fires.

The illuminating rocket (Fig. 17) consists of a sheet iron cartridge, a, containing a composition designed to give it motion, of a cylinder, b, of sheet iron, capped with a cone of the same material and containing illuminating stars of Lamarre composition and an explosive for expelling them, and, finally, of a directing stick, c. Priming is effected by means of a bunch of quickmatches inclosed in a cardboard tube placed in contact with the propelling composition. This latter is the same as that used in signal rockets. As in the case of the latter, a space is left in the axis of the cartridges. These rockets are fired from a trough placed at an inclination of fifty or sixty degrees. Those of three inches illuminate the earth for a distance of 900 yards. They may be used to advantage in the operation of signaling.

A parachute fire is a device designed to be ejected from a pot at the end of the rocket's travel, and to emit a bright light during its slow descent. It consists of a small cylindrical cardboard box (Fig. 16) filled with common star paste or Lamarre stars, and attached to a parachute, e, by means of a small brass chain, d.

To make this parachute, we cut a circle ten feet in diameter out of a piece of calico, and divide its circumference into ten or twelve equal parts. At each point of division we attach a piece of fine hempen cord about three feet in length, and connect these cords with each other, as well as with the suspension chain, by ligatures that are protected against the fire by means of balls of sized paper.

In rockets designed to receive these parachutes, a small cavity is reserved at the extremity of the cartridge for the reception of 225 grains of powder. To fill the pot, the chain, d, is rolled spirally around the box, c, and the latter is covered with the parachute, e, which has been folded in plaits, and then folded lengthwise alternately in one direction and the other.

The parachute port-fire consists of a cardboard tube of from quarter to half an inch in diameter, and from four to five inches in length, closed at one extremity and filled with star paste. This is connected by a brass wire with a cotton parachute eight inches in diameter. A rocket pot is capable of holding twenty of these port-fires.

Parachute fires and port-fires are used to advantage in the operation of signaling.—La Nature.

* * * * *



IMPROVEMENT IN LAYING OUT FRAMES OF VESSELS—THE FRAME TRACER.

By GUSTAVE SONNENBURG.

To avoid the long and time-consuming laying out of a boat by ordinates and abscissas, I have constructed a handy apparatus, by which it is possible without much trouble to obtain the sections of a vessel graphically and sufficiently accurate. The description of its construction is given with reference to the accompanying cut. A is a wooden rod of rectangular section, to which are adapted two brackets, a_{1} a_{2}, lined with India rubber or leather; a_{1} is fixed to the wood, a_{2} is of metal, and, like the movable block of a slide gauge, moves along A. In the same plane is a second rod, perpendicular to A, and attached thereto, which is perforated by a number of holes. A revolving pin, C, is adapted to pass through these holes, to which a socket, D, is pivoted, C acting as its axis. To prevent this pin from falling out, it is secured by a nut behind the rod. Through the socket, D, runs a rod, E, which carries the guide point, s_{1}, and pencil, s_{2}. Over s_{1} a rubber band is stretched, to prevent injury to the varnish of the boat. Back of and to A and B a drawing board is attached, over which a sheet of paper is stretched.



The method of obtaining a section line is as follows: The rod, A, is placed across the gunwale and perpendicular to the axis of the boat, and its anterior vertical face is adjusted to each frame of the boat which it is desired to reproduce. By means of the brackets, a_{1} and a_{2}, A is fixed in place. The bolt, C, is now placed in the perforations already alluded to, which are recognized as most available for producing the constructional diagram. At the same time the position of the pencil point, s_{2}, must be chosen for obtaining the best results.

Next the operator moves along the side of the boat the sharpened end, s{1}, of the rod, E, and thus for the curve from keel to gunwale, s{2} describes a construction line. It is at once evident that a{2}, for example, corresponds to the point, a{1}. The apparatus is now removed and placed on the working floor. If, reversing things, the point, s{1}, is carried around the construction curve, the point, s{2}, will inscribe the desired section in its natural dimensions. This operation is best conducted after one has chosen and described all the construction curves of the boat. Next, the different section lines are determined, one by one, by the reversed method above described. The result is a half section of the boat; the other symmetrical half is easily obtained.

If the whole process is repeated for the other side of the boat, tracing paper being used instead of drawing paper, the boat may be tested for symmetry of building, a good control for the value of the ship. For measuring boats, as for clubs and regattas, for seamen, and often for the so-called Spranzen (copying) of English models, my apparatus, I doubt not, will be very useful.—Neuste Erfindungen und Erfahrungen.

* * * * *



TAR FOR FIRING RETORTS.

The attention of gas engineers has been forcibly directed to the use of tar as a fuel for the firing of retorts, now that this once high-priced material is suffering, like everything else (but, perhaps, to a more marked extent), by what is called "depression in trade." In fact, it has in many places reached so low a commercial value that it is profitable to burn it as a fuel. Happily, this is not the case at Nottingham; and our interest in tar as a fuel is more experimental, in view of what may happen if a further fall in tar products sets in. I have abandoned the use of steam injection for our experimental tar fires in favor of another system. The steam injectors produce excellent heats, but are rather intermittent in their action, and the steam they require is a serious item, and not always available.



Tar being a pseudo liquid fuel, in arranging for its combustion one has to provide for the 20 to 25 per cent. of solid carbon which it contains, and which is deposited in the furnace as a kind of coke or breeze on the distillation of the volatile portions, which are much more easily consumed than the tar coke.

THE TAR FIRE

I have adopted is one that can be readily adapted to an ordinary coke furnace, and be as readily removed, leaving the furnace as before. The diagram conveys some idea of the method adopted. An iron frame, d, standing on legs on the floor just in front of the furnace door, carries three fire tiles on iron bearers. The top one, a, is not moved, and serves to shield the upper face of the tile, b, from the fierce heat radiated from the furnace, and also causes the air that rushes into the furnace between the tiles, a and b, to travel over the upper face of the tile, b, on which the tar flows, thereby keeping it cool, and preventing the tar from bursting into flame until it reaches the edge of the tile, b, over the whole edge of which it is made to run fairly well by a distributing arrangement. A rapid combustion takes place here, but some unconsumed tar falls on to the bed below. About one-third of the grate area is filled up by a fire tile, and on this the tar coke falls. The tile, c, is moved away from time to time, and the tar coke that accumulates in front of it is pushed back on to the fire bars, e, at the back of the furnace, to be there consumed. Air is thus admitted, by three narrow slot-like openings, to the front of the furnace between the tiles, a, b, and c, and under c and through the fire bars, e. The air openings below are about three times the area of the openings in the front of the furnace; but as the openings between the fire bars and the tiles are always more or less covered by tar coke, it is impossible to say what the effective openings are. This disposition answers admirably, and requires little attention. Three minutes per hour per fire seems to be the average, and the labor is of a very light kind, consisting of clearing the passages between the tiles, and occasionally pushing back the coke on to the fire bars. These latter are not interfered with, and will not require cleaning unless any bricks in the furnace have been melted, when a bed of slag will be found on them.

THE AMOUNT OF DRAUGHT

required for these fires is very small, and less than with coke firing. I find that 0.08 in. vacuum is sufficient with tar fires, and 0.25 in. for coke fires. The fires would require less attention with more draught and larger tar supply, as the apertures do not so easily close with a sharp draught, and the tar is better carried forward into the furnace. A regular feed of tar is required, and considerable difficulty seems to have been experienced in obtaining this. So long as we employed ordinary forms of taps or valves, so long (even with filtration) did we experience difficulties with the flow of viscous tar. But on the construction of valves specially designed for the regulation of its flow, the difficulty immediately disappeared, and there is no longer the slightest trouble on this account. The labor connected with the feeding of furnaces with coke and cleaning fires from clinker is of a very arduous and heavy nature. Eight coke fires are normally considered to be work for one man. A lad could work sixteen of these tar fires.

COMPOSITION OF FURNACE GASES.

Considerable attention has been paid to the composition of the furnace gases from the tar fires. The slightest deficiency in the air supply, of course, results in the immediate production of smoke, so that the damper must be set to provide always a sufficient air supply. Under these circumstances of damper, the following analyses of combustion gases from tar fires have been obtained:

No Smoke. CO_{2}. O. CO. 11.7 5.0 Not determined. 13.3 3.7 " 10.8 5.4 " 14.8 2.5 " 13.5 3.0 " 12.4 5.6 " 12.4 4.6 " 13.1 5.9 " 15.3 1.0 " 10.8 4.0 " 14.0 2.8 " _ _ Average 12.9 3.9 (11 analyses) _ _ 11.5 Not determined. 14.3 " 14.6 "

Damper adjusted so that a slight smoke was observable in the combustion gases.

CO_{2}. O. CO. 17.30 None. Not determined. 16.60 " " 16.50 0.1 " 15.80 0.1 " 16.20 1.8 0.7 __ __ __ Average 16.48 0.4 0.7

—Gas Engineer.

* * * * *



A NEW MERCURY PUMP.

The mercury pumps now in use, whether those of Geissler, Alvergniat, Toepler, or Sprengel, although possessed of considerable advantages, have also serious defects. For instance, Geissler's pump requires a considerable number of taps, that of Alvergniat and Toepler is very fragile in consequence of its complicated system of tubes connected together, and that of Sprengel is only suitable for certain purposes.

The new mercury pump constructed by Messrs. Greisser and Friedrichs, at Stutzerbach, is remarkable for simplicity of construction and for the ease with which it is manipulated, and also because it enables us to arrive at a perfect vacuum.

The characteristic of this pump is, according to La Lumiere Electrique, a tap of peculiar construction. It has two tubes placed obliquely in respect to its axis, which, when we turn this tap 90 or 180 degrees, are brought opposite one of the three openings in the body of the tap.

Thus the striae that are formed between the hollowed-out parts of the tap do not affect its tightness; and, besides, the turns of the tap have for their principal positions 90 and 180 degrees, instead of 45 and 90 degrees, as in Geissler's pump.

The working of the apparatus, which only requires the manipulation of a single tap, is very simple. When the mercury is raised, the tap is turned in such a manner that the surplus of the liquid can pass into the enlarged appendage, a, placed above the tap, and communication is then cut off by turning the tap to 90 degrees.

The mercury reservoir having descended, the bulb empties itself, and then the tap is turned on again, in order to establish communication with the exhausting tube. The tap is then closed, the mercury ascends again, and this action keeps on repeating.



* * * * *

NO ELECTRICITY FROM THE CONDENSATION OF VAPOR.—It has been maintained by Palmieri and others that the condensation of vapor results in the production of an electrical charge. Herr S. Kalischer has renewed his investigations upon this point, and believes that he has proved that no electricity results from such condensation. Atmospheric vapor was condensed upon a vessel coated with tin foil, filled with ice, carefully insulated, and connected with a very sensitive electrometer. No evidence could be obtained of electricity.—Ann. der Physik und Chemie.

* * * * *



THE ELECTRO-MAGNETIC TELEPHONE TRANSMITTER.

An interesting contribution was made by M. Mercadier in a recent number of the Comptes Rendus de l'Academie Francaise. On the ground of some novel and some already accepted experimental evidence, M. Mercadier holds that the mechanism by virtue of which the telephonic diaphragms execute their movements is analogous to, if not identical with, that by which solid bodies of any form, a wall for instance, transmit to one of their surfaces all the vibratory movements of any kind which are produced in the air in contact with the other surface. It is a phenomenon or resonance. Movements corresponding to particular sounds may be superposed in slender diaphragms, but this superposition must necessarily be disturbing under all but exceptional circumstances. In proof of this view, it is cited that diaphragms much too rigid, or charged with irregularly distributed masses over the surface, or pierced with holes, or otherwise evidently unfitted for the purpose, are available for transmission. They will likewise serve when feathers, wool, wood, metals, mica, and other substances to the thickness of four inches are placed between the diaphragm and the source of vibratory movement. The magnetic field does not alter these relations in any way. The real diaphragm may be removed altogether. It is sufficient to replace it by a few grains of iron filings thrown on the pole covered with a piece of pasteboard or paper. Such a telephone works distinctly although feebly; but any slender flexible disk, metallic or not, spread over across the opening of the cover of the instrument, with one or two tenths of a gramme (three grains) of iron filings, will yield results of increased and even ordinary intensity. This is the iron filing telephone, which is reversible; for a given magnetic field there is a certain weight of iron filings for maximum intensity. It appears thus that the advantage of the iron diaphragm over iron filings reduces itself to presenting in a certain volume a much more considerable number of magnetic molecules to the action of the field. The iron diaphragm increases the telephonic intensity, but it is by no means indispensable.

* * * * *



ON ELECTRO-DISSOLUTION, AND ITS USE AS REGARDS ANALYSIS.

By H.N. WARREN, Research Analyst.

On the same principle that electro-dissolution is used for the estimation of combined carbon in steel, etc., I have lately varied the experiment by introducing, instead of steel, iron containing a certain percentage of boron, and, having connected the respective boride with the positive pole of a powerful battery, and to the negative a plate of platinum, using as a solvent dilute sulphuric acid, I observed, after the lapse of about twelve hours, the iron had entirely passed into solution, and a considerable amount of brownish precipitate had collected at the bottom of the vessel, intercepted by flakes of graphite and carbon; the precipitate, having been collected on a filter paper, washed, and dried, on examination proved to be amorphous boron, containing graphite and other impurities, which had become chemically introduced during the preparation of the boron compound. The boron was next introduced into a small clay crucible, and intensely heated in a current of hydrogen gas, for the purpose of rendering it more dense and destroying its pyrophoric properties, and was lastly introduced into a combustion tubing, heated to bright redness, and a stream of dry carbonic anhydride passed over it, in order to separate the carbon, finally pure boron being obtained.

In like manner silicon-eisen, containing 9 per cent. of silicon, was treated, but not giving so satisfactory a result. A small quantity only of silicon separates in the uncombined form, the greater quantity separating in the form of silica, SiO_{2}, the amorphous silicon so obtained apparently being more prone to oxidation than the boron so obtained.

Ferrous sulphide was next similarly treated, and gave, after the lapse of a few hours, a copious blackish precipitation of sulphur, and possessing properties similar to the sulphur obtained by dissolving sulphides such as cupric sulphide in dilute nitric acid, in all other respects resembling common sulphur.

Phosphides of iron, zinc, etc., were next introduced, and gave, besides carbon and other impurities, a residue containing a large percentage of phosphorus, which differed from ordinary phosphorus with respect to its insolubility in carbon disulphide, and which resembled the reaction in the case with silicon-eisen rather than that of the boron compound, insomuch that a large quantity of the phosphorus had passed into solution.

A rod of impure copper, containing arsenic, iron, zinc, and other impurities, was next substituted, using hydrochloric acid as a solvent in place of sulphuric acid. In the course of a day the copper had entirely dissolved and precipitated itself on the negative electrode, the impurities remaining in solution. The copper, after having been washed, dried, and weighed, gave identical results with regard to percentage with a careful gravimetric estimation. I have lately used this method, and obtained excellent results with respect to the analysis of commercial copper, especially in the estimation of small quantities of arsenic, thus enabling the experimenter to perform his investigation on a much larger quantity than when precipitation is resorted to, at the same time avoiding the precipitated copper carrying down with it the arsenic. I have in this manner detected arsenic in commercial copper when all other methods have totally failed. I have also found the above method especially applicable with respect to the analysis of brass.

With respect to ammoniacal dissolution, which I will briefly mention, a rod composed of an alloy of copper and silver was experimented upon, the copper becoming entirely dissolved and precipitating itself on the platinum electrode, the whole of the silver remaining suspended to the positive electrode in an aborescent form. Arsenide of zinc was similarly treated, the arsenic becoming precipitated in like manner on the platinum electrode. Various other alloys, being experimented upon, gave similar results.

I may also, in the last instance, mention that I have found the above methods of electro-dissolution peculiarly adapted for the preparation of unstable compounds such as stannic nitrate, potassic ferrate, ferric acetate, which are decomposed on the application of heat, and in some instances have succeeded by the following means of crystallizing the resulting compound obtained.—Chem. News.

* * * * *



A NEWLY DISCOVERED SUBSTANCE IN URINE.

Dr. Leo's researches on sugar in urine are interesting, and tend to correct the commonly accepted views on the subject. Professor Scheibler, a chemist well known for his researches on sugar, has observed that the determination of the quantity of that substance contained in a liquid gives different results, according as it is done by Trommer's method or with the polariscope. As sugar nowadays is exclusively dealt with according to the degree of polarization, this fact is of enormous value in trade. Scheibler has isolated a substance that is more powerful in that respect than grape sugar. Dr. Leo's researches yield analogous results, though in a different field. He has examined a great quantity of diabetic urine after three different methods, namely, Trommer's (alkaline solution of copper); by fermentation; and with the polarization apparatus. In many cases the results agreed, while in others there was a considerable difference.

He succeeded in isolating a substance corresponding in its chemical composition to grape sugar, and also a carbo-hydrate differing considerably from grape sugar, and turning the plane of polarization to the left. The power of reduction of this newly discovered substance is to that of grape sugar as 1:2.48. Dr. Leo found this substance in three specimens of diabetic urine, but it was absent in normal urine, although a great amount was examined for that purpose. From this it may be concluded that the substance does not originate outside the organism, and that it is a pathological product. The theory of Dr. Jaques Meyer, of Carlsbad, that it may be connected with obesity, is negatived by the fact that of the three persons in whom this substance was found, only one was corpulent.

* * * * *



FURNACE FOR DECOMPOSING CHLORIDE OF MAGNESIUM.



The problem of decomposing chloride of magnesium is one which has attracted the attention of technical chemists for many years. The solution of this problem would be of great importance to the alkali trade, and, consequently, to nearly every industry. The late Mr. Weldon made many experiments on this subject, but without any particular success. Of late a furnace has been patented in Germany, by A. Vogt, which is worked on a principle similar to that applied to salt cake furnaces; but with this difference, that in place of the pot it has a revolving drum, and instead of the roaster a furnace with a number of shelves. The heating gases are furnished by a producer, and pass from below upward over the shelves, S, then through the channel, C, into the drum, D, which contains the concentrated chloride of magnesium. When the latter has solidified, but before being to any extent decomposed, it is removed from the drum and placed on the top shelf of the furnace. It is then gradually removed one shelf lower as the decomposition increases, until it arrives at the bottom shelf, where it is completely decomposed in the state of magnesia, which is emptied through, E. The drum, D, after being emptied, is again filled with concentrated solution of chloride of magnesium. The hydrochloric acid leaves through F and G. If, instead of hydrochloric acid, chlorine is to be evolved, it is necessary to heat the furnace by means of hot air, as otherwise the carbonic acid in the gases from the generator would prevent the formation of bleaching powder. The air is heated in two regenerating chambers, which are placed below the furnace.—Industries.

* * * * *



THE FILTRATION AND THE SECRETION THEORY.

At a recent meeting of the Physiological Society, Dr. J. Munk reported on experiments instituted by him in the course of the last two years with a view of arriving at an experimental decision between the two theories of the secretion of urine—the filtration theory of Ludwig and the secretion theory of Heidenhain. According to the first theory, the blood pressure prescribed the measure for the urine secretion; according to the second theory, the urine got secreted from the secretory epithelial cells of the kidneys, and the quantity of the matter secreted was dependent on the rate of movement of the circulation of the blood. The speaker had instituted his experiments on excided but living kidneys, through which he conducted defibrinized blood of the same animals, under pressures which he was able to vary at pleasure between 80 mm. and 190 mm. Fifty experiments on dogs whose blood and kidneys were, during the experiment, kept at 40 deg. C., yielded the result that the blood of starving animals induced no secretion of urine, which on the other hand showed itself in copious quantities where normal blood was conducted through the kidney. If to the famished blood was added one of the substances contained as ultimate products of digestion in the blood, such, for example, as urea, then did the secretion ensue.

The fluid dropping from the ureter contained more urea than did the blood. That fluid was therefore no filtrate, but a secretion. An enhancement of the pressure of the blood flowing through the kidney had no influence on the quantity of the secretion passing away. An increased rate of movement on the part of the blood, on the other hand, increased in equal degree the quantity of urine. On a solution of common salt or of mere serum sanguinis being poured through the kidney, no secretion followed. All these facts, involving the exclusion of the possibility of a central influence being exercised from, the heart or from the nervous system on the kidneys, were deemed by the speaker arguments proving that the urine was secreted by the renal epithelial cells. A series of diuretics was next tried, in order to establish whether they operated in the way of stimulus centrally on the heart or peripherally on the renal cells. Digitalis was a central diuretic. Common salt, on the other hand, was a peripheral diuretic. Added in the portion of 2 per cent. to the blood, it increased the quantity of urine eight to fifteen fold. Even in much less doses, it was a powerful diuretic. In a similar manner, if yet not so intensely, operated saltpeter and coffeine, as also urea and pilocarpine. On the introduction, however, of the last substance into the blood, the rate of circulation was accelerated in an equal measure as was the quantity of urine increased, so that in this case the increase in the quantity of urine was, perhaps, exclusively conditioned by the greater speed in the movement of the blood. On the other hand, the quantity of secreted urine was reduced when morphine or strychine was administered to the blood. In the case of the application of strychnine, the rate in the current of the blood was retarded in a proportion equal to the reduction in the secretion of the urine.

The speaker had, finally, demonstrated the synthesis of hippuric acid and sulphate of phenol in the excided kidney as a function of its cells, by adding to the blood pouring through the kidney, in the first place, benzoic acid and glycol; in the second place, phenol and sulphate of soda. In order that these syntheses might make their appearance in the excided kidney, the presence of the blood corpuscles was not necessary, though, indeed, the presence of oxygen in the blood was indispensable.

* * * * *



VARYING CYLINDRICAL LENS.

By TEMPEST ANDERSON, M.D., B. Sc.

The author has had constructed a cylindrical lens in which the axis remains constant in direction and amount of refraction, while the refraction in the meridian at right angles to this varies continuously.

A cone may be regarded as a succession of cylinders of different diameters graduating into one another by exceedingly small steps, so that if a short enough portion be considered, its curvature at any point may be regarded as cylindrical. A lens with one side plane and the other ground on a conical tool is therefore a concave cylindrical lens varying in concavity at different parts according to the diameter of the cone at the corresponding part. Two such lenses mounted with axes parallel and with curvatures varying in opposite directions produce a compound cylindrical lens, whose refraction in the direction of the axes is zero, and whose refraction in the meridian at right angles to this is at any point the sum of the refractions of the two lenses. This sum is nearly constant for a considerable distance along the axis so long as the same position of the lenses is maintained. If the lenses be slid one over the other in the direction of their axes, this sum changes, and we have a varying cylindrical lens. The lens is graduated by marking on the frame the relative position of the lenses when cylindrical lenses of known power are neutralized.

Lenses were exhibited to the Royal Society, London, varying from to -6 DCy, and from to +6 DCy.

* * * * *



THE LAWS OF THE ABSORPTION OF LIGHT IN CRYSTALS.

By H. BECQUEREL.

1. The absorption spectrum observed through a crystal varies with the direction of the rectilinear luminous vibration which propagates itself in this crystal. 2. The bands or rays observed through the same crystal have, in the spectrum, fixed positions, their intensity alone varying. 3. For a given band or ray there exist in the crystal three rectangular directions of symmetry, according to one of which the band generally disappears, so that for a suitable direction of the luminous vibrations the crystal no longer absorbs the radiations corresponding to the region of the spectrum where the band question appeared. These three directions may be called the principal directions of absorption, relative to this band. 4. In the orthorhombic crystals, by a necessary consequence of crystalline symmetry, the principal directions of absorption of all the bands coincide with the three axes of symmetry. We may thus observe three principal absorption spectra. In uniaxial crystals the number of absorption spectra is reduced to two. 5. In clinorhombic crystals one of the principal directions of absorption of each crystal coincides with the only axis of symmetry; the two other principal rectangular directions of each band may be found variously disposed in the plane normal to this axis. Most commonly these principal directions are very near to the principal corresponding directions of optical elasticity. 6. In various crystals the characters of the absorption phenomena differ strikingly from those which we might expect to find after an examination of the optical properties of the crystal. We have just seen that in clinorhombic crystals the principal absorption directions of certain bands were completely different from the axis of optical elasticity of the crystal for the corresponding radiations. If we examine this anomaly, we perceive that the crystals manifesting these effects are complex bodies, formed of various matters, one, or sometimes several, of which absorb light and give each different absorption bands. Now, M. De Senarmont has shown that the geometric isomorphism of certain substances does not necessarily involve identity of optical properties, and in particular in the directions of the axes of optical elasticity in relation to the geometric directions of the crystal. In a crystal containing a mixture of isomorphous substances, each substance brings its own influence, which may be made to predominate in turn according to the proportions of the mixture. We may, therefore, admit that the molecules of each substance enter into the crystal retaining all the optical properties which they would have if each crystallized separately. The principal directions of optical elasticity are given by the resultant of the actions which each of the component substances exerts on the propagation of light, while the absorption of a given region of the spectrum is due to a single one of these substances, and may have for its directions of symmetry the directions which it would have in the absorbing molecule supposing it isolated. It may happen that these directions do not coincide with the axes of optical elasticity of the compound crystal. If such is the cause of the anomaly of certain principal directions of absorption, the bands which present these anomalies must belong to substances different from those which yield bands having other principal directions of absorption. If so, we are in possession of a novel method of spectral analysis, which permits us to distinguish in certain crystals bands belonging to different matters, isomorphous, but not having the same optical properties. Two bands appearing in a crystal with common characters, but presenting in another crystal characters essentially different, must also be ascribed to two different bodies.

* * * * *

[Continued from SUPPLEMENT, No. 585, page 9345.]



HISTORY OF THE WORLD'S POSTAL SERVICE.

It is commonly believed in Europe that the mail is chiefly forwarded by the railroads; but this is only partially the case, as the largest portion of the mails is intrusted now, as formerly, to foot messengers. How long this will last is of course uncertain, as the present postal service seems suitable enough for the needs of the people. The first task of the mail is naturally the collection of letters. Fig. 17 represents a letter box in a level country.



By way of example, it is not uninteresting to know that the inhabitants of Hanover in Germany made great opposition to the introduction of letter boxes, for the moral reason that they could be used to carry on forbidden correspondence, and that consequently all letters should be delivered personally to the post master.

After the letters are collected, the sorting for the place of destination follows, and Fig. 18 represents the sorting room in the Berlin Post Office. A feverish sort of life is led here day and night, as deficient addresses must be completed, and the illegible ones deciphered.

It may here be mentioned that the delivery of letters to each floor of apartment houses is limited chiefly to Austria and Germany. In France and England, the letters are delivered to the janitor or else thrown into the letter box placed in the hall.

After the letters are arranged, then comes the transportation of them by means of the railroad, the chaise, or gig, and finally the dog mail, as seen in Fig. 19. It is hard to believe that this primitive vehicle is useful for sending mail that is especially urgent, and yet it is used in the northern part of Canada. Drawn by three or four dogs, it glides swiftly over the snow.

It is indeed a large jump from free America, the home of the most unlimited progress, into the Flowery Kingdom, where cues are worn, but we hope our readers are willing to accompany us, in order to have the pleasure of seeing how rapidly a Chinese mail carrier (Fig. 20) trots along his route under his sun umbrella.

Only the largest and most robust pedestrians are chosen for service, and they are obliged to pass through a severe course of training before they can lay any claim to the dignified name, "Thousand Mile Horse."