The inclined tray shown at the top of the furnace on Fig. 1 is made of the same material as the furnace itself, and when kneaded into shape is supported on a wooden framework. On it is piled a supply of charcoal, which is raked into the furnace when required.

The blowing apparatus is singularly ingenious, and is certainly as economical of manual labor as a blowing arrangement depending on manual labor well can be. A section of the bellows forms the portion to the right of Fig. 1, showing tuyere forming the connection between bellows and furnace. It consists of a circular segment of hard wood, rudely hollowed, and having a piece of buffalo hide with a small hole in its center tied over the top. Into this hole a strong cord is passed, with a small piece of wood attached to the end to keep it inside the bellows, while the other end is attached to a bent bamboo firmly fixed into the ground close by. This bamboo acts as a spring, drawing up the string, and consequently the leather cover of the bellows, to its utmost stretch, while air enters through the central hole. When thus filled, a man places his foot on the hide, closing the central hole with his heel, and then throwing the whole weight of his body on to that foot, he depresses the hide, and drives the air out through a bamboo tube inserted in the side and communicating with the furnace. At the same time he pulls down the bamboo with the arm of that side. Two such bellows are placed side by side, a thin bamboo tube attached to each, and both entering the one tuyere; and so by jumping on each bellows alternately, the workman keeps up a continuous blast.



The Figs. 1 and 2 are taken from sketches, and the description from particulars, by Mr. Blandford, who was for some years on the Geological Survey of India, and had exceptional opportunities in his journeyings of observing the customs and occupations of the Indian iron smelters. The blowing machine is an especially wonderful and effective machine, and was first described and illustrated by Mr. Robert Rose, in a Calcutta publication, more than half a century ago. He also had seen it used in iron making in India.—Colliery Guardian.

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WOOD OIL.

Wood oil is now made on a large scale in Sweden from the refuse of timber cuttings and forest clearings, and from stumps and roots. Although it cannot well be burned in common lamps, on account of the heavy proportion of carbon it contains, it is said to furnish a satisfactory light in lamps specially made for it; and in its natural state it is the cheapest illuminating oil. There are some thirty factories engaged in its production, and they turn out about 40,000 liters of the oil daily. Turpentine, creosote, acetic acid, charcoal, coal-tar oils, etc., are also obtained from the same materials as the wood oil.

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SOAP.

By HENRY LEFFMANN, M.D.

Although the use of soap dates from a rather remote period, the chemist is still living, at an advanced age, to whom we are indebted for a knowledge of its composition and mode of formation. Considerably more than a generation has elapsed since Chevreul announced these facts, but a full appreciation of the principles involved is scarcely realized outside of the circle of professional chemists. Learned medical and physiological writers often speak of glycerin as the "sweet principle of fats," or term fats compounds of fatty acids and glycerin. Indeed, there is little doubt that the great popularity of glycerin as an emollient arose from the view that it represented the essential base of the fats. With regard to soap, also, much erroneous and indistinct impression prevails. Its detergent action is sometimes supposed to be due to the free alkali, whereas a well-made soap is practically neutral.

A desire to secure either an increased detergent, cleansing, or other local effect has led in recent years to the introduction into soaps of a large number of substances, some of which have been chosen without much regard to their chemical relations to the soap itself. The result has been the enrichment of the materia medica with a collection of articles of which some are useful, and others worse than useless. The extension of the list of disinfectant and antiseptic agents and the increased importance of the agents, in surgery, have naturally suggested the plan of incorporating them with soaps, in which form they will be most convenient for application. Accordingly, the circulars of the manufacturing pharmacists have prominently displayed the advantages of various disinfecting soaps.

Among these is a so-called corrosive sublimate soap, of which several brands are on sale. One of these, containing one per cent. of corrosive sublimate, is put on the market in cakes weighing about sixteen hundred grains, and each cake, therefore, contains sixteen grains of the drug—a rather large quantity, perhaps, when it is remembered that four grains is a fatal dose. Fortunately, however, for the prevention of accidents, but unfortunately for the therapeutic value of the soap, a decomposition of the sublimate occurs as soon as it is incorporated in the soap mass, by which an insoluble mercurial soap is formed. This change takes place independently of the alkali used in the soap; in fact, as mentioned above, a well-made soap contains no appreciable amount of free alkali, but is due to the action of the fat acids. Corrosive sublimate is incompatible with any ordinary soap mass, and this incompatibility includes not only other soluble mercurial salts, but also almost all the mineral antiseptics, such as zinc chloride, copper sulphate, iron salts. Some of the preparations of arsenic may, however, be incorporated with soap without decomposition.

Such being the chemical facts, we must admit that no reliance can be placed in corrosive sublimate soaps as germicide agents. It must not be supposed that this incompatibility interferes with the use of these soaps for general therapeutic purposes. It is only the specific germicide value which is destroyed. Since the fats used in soap manufacture yield oleic acid, we will have a certain amount of mercuric oleates formed together with stearate and other salts, and for purposes of inunction these salts might be efficient. Still the physician would prefer, doubtless, to use the specially prepared mercurial.

In producing, therefore, a disinfecting soap, being debarred from using the metallic germicides, we are fortunate in the possession of a number of efficient agents, organic in character, which may be used without interference in soaps.

Among these are thymol, naphthol, oil of eucalyptus, carbolates, and salicylates. There is no chemical incompatibility of these with soap, and as they are somewhat less active, weight for weight, than corrosive sublimate, they are capable of use in larger quantities with less danger, and can thus be made equally efficacious.

It is in this direction, therefore, that we must look for the production of a safe and reliable antiseptic soap.

There is not much exact knowledge as to the usefulness of such additions to soap as borax and glycerin. They are frequently added, and highly spoken of in advertisements. Borax is a mild alkaline body, and as a detergent is probably equivalent to a slight excess of caustic soda. Glycerin, although originally considered an emollient, probably on account of its source and physical properties, is in reality, to some skins at least, a slight irritant. It is, in fact, an alcohol, not a fat. It does not pre-exist in fats, but is formed when the fat is decomposed by alkali or steam.

In ordinary cases, soap owes its detergent effect to a decomposition which occurs when it is put in water.

A perfectly neutral soap, that is, one which contains the exact proportion of alkali and fat acid, will, when placed in cold water, decompose into two portions, one containing an excess of the acid, the other an excess of alkali. The latter dissolves, and gives a slightly alkaline solution; the former precipitates, and gives the peculiar turbidity constituting "suds." These reactions must be kept in mind in determining the effect of the addition of any special substance to the soap.—The Polyclinic.

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OPTICAL ERRORS AND HUMAN MISTAKES.[1]

[Footnote 1: Read before the American Association, Buffalo, August, 1886.]

By ERNST GUNDLACH.

I wish to call attention to a few mistakes that are quite commonly made by microscopists and writers in stating the result of their optical tests of microscope objectives.

If the image of an object as seen in the microscope appears to be unusually distorted and indistinct toward the edge of the field, and satisfactory definition is limited to a small portion of the center, the cause is often attributed to the spherical aberration of the objective, while really this phenomenon has nothing to do with that optical defect of the objective, if any exists, but is caused by a lack of optical symmetry. If a perfectly symmetrical microscope objective could be constructed, then, with any good eye-piece, it would make no difference to the definition of the object were it placed either in the center or at the edge of the field, even if the objective had considerable spherical aberration. But, unfortunately, our most symmetrical objectives, the low powers, leave much to be desired in this respect, while our wide angle, high powers are very far from symmetrical perfection.

There are two causes of this defect in the latter objectives, one being the extreme wideness of their angular apertures, and the other the great difference in the distances of the object and the image from the optical center of the objectives.

Another mistake is often made in regard to the cause of certain prismatic colors that are sometimes, in a striking degree, produced by otherwise good objectives. According to the nature of these colors, whether yellow or blue, green or indigo, they are generally regarded as evidences of either chromatic over or under correction of the objective. Of course the presence of either of these defects is certainly and correctly indicated by the appearance of one or the other of the colors, under certain circumstances; but the simple visibility of prismatic color is by no means a reliable indication of over or under correction of color, and, indeed, to the honor of our opticians, it may be stated that very few objectives are made that cannot justly be called achromatic in the general sense of the term. By far the most common causes of prismatic color, in otherwise carefully constructed objectives, are the so-called chromatic aberrations of second or higher order. Every achromatic lens which is, as it should be, at its best at about two-thirds of its aperture, is inside of this ring or zone, toward the center slightly under and outside, toward the edge, slightly over corrected. This defect is the greater, the less the difference of the dispersive powers of the two glasses used in the construction of the lens, for a given proportion of their refractive indexes, and therefore the degree of visibility of the colors of the aberrations of the second order depends greatly on the nature of the glass employed in the construction of the lens.

This defect may be corrected by a suitable combination of two or more lenses, though not without again having similarly, as in the correction of the first color, some faint remnants of color, the aberrations of third or still higher order. But even the correction of the third or still higher order may, if the angular aperture is very wide, leave quite visible and disturbing remnants of color.

Another and not uncommon explanation of the cause of this unwelcome color, though not so serious and damaging a charge to the maker of the objectives, is its attribution to the so-called "secondary spectrum." This error, like that previously mentioned, is certainly indicated by the appearance of certain colors under certain conditions, but being, as a rule, one of the least defects of even our best objectives in most cases, it is probably not the true source of the disturbance.

The secondary spectrum is very commonly confounded with the chromatic aberration of higher order. While the latter is produced by imperfections in the form of the lens, the former is due to an imperfection of the optical qualities of the material from which the lens is constructed, the crown and flint glass.

A glass prism of any angle will project upon a white surface a spectrum of any length, according to the arrangement of the light source, the screen, and the prism. So with two prisms of the same kind of glass, but of different angles, two spectra can be produced of exactly equal length, so that if one is brought over the other, with the corresponding colors in line, they will appear as one spectrum. But if one of the prisms is made of crown and the other of flint glass, then their spectra cannot be arranged so that all their corresponding colors would be in line, for the proportional distances of the different colors differ in the two spectra. If two colors of the spectra are, by suitable arrangement, brought exactly in line, then the others will be out. The two spectra do not coincide, and the result, if an achromatic lens be made of these glasses, must be a remnant of color which cannot be neutralized. This remnant is the secondary spectrum.

Although this peculiar disharmony in the dispersive powers of the two glasses, crown and flint, was discovered almost immediately after achromatism was invented, it was only recently that the first successful attempts were made to produce different glasses, which, possessing the other requirements for achromatic objectives, would produce coincident spectra, or nearer so than the ordinary crown and flint glass do. It was about twelve years ago, if my memory serves me, when I learned that a well-known English firm, engaged in the manufacture of optical glass, had brought out some new glass possessed of the desired qualities, and a little later I received a circular describing the glass. But at the same time I learned that the new glass was very soft and difficult to polish, and also that it had to be protected from the atmosphere, and further, that an English optician had failed to construct an improved telescope objective from it. I had ordered some samples of the glass, but never received any.

A few months ago, news from Europe reached this country that another and seemingly more successful attempt had been made to produce glass that would leave no secondary spectrum, and that Dr. Zeiss, the famous Jena optician, had constructed some new improved objectives from it. But the somewhat meager description of these objectives, as given by an English microscopist, did not seem fit to excite much enthusiasm here as to their superiority over what had already been done in this country. Besides this, the report said that the new objectives were five system, and also that extra eye-pieces had to be used with them. I confess I am much inclined to attribute the optical improvement, which, according to Dr. Abbe's own remark, is very little, more to the fact that the objectives are five system than to the new glass used in their construction.

After a close study of a descriptive list of the new glass, received a week or two ago from the manufacturers, I find, to my great regret, that this new glass seems to suffer from a similar weakness to that made by the English firm twelve years ago; as all the numbers of the list pointed out by the makers as having a greatly reduced secondary spectrum are accompanied with the special remark "to be protected." Furthermore, from a comparison of the dispersive and refractive powers of these glasses, as given in the list, I find that objectives constructed from them will leave so great aberrations of higher order, both spherical and chromatic, that the gain by the reduction of the secondary spectrum would be greatly overbalanced.

In conclusion, I wish to say that while I would beware of underestimating the great scientific and practical value of the endeavor of the new German glass makers to produce improved optical glass, and the great benefit accruing to opticians and all others interested in the use of optical instruments, I think it wise not to overestimate the real value of the defects of the common crown and flint glass, which I have sought to explain in this paper. And, for myself, I prefer to fight the more serious defects first, and when its time has come I will see what can be done with the secondary spectrum.

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PROBABLE ISOLATION OF FLUORINE. DECOMPOSITION OF HYDROFLUORIC ACID BY AN ELECTRIC CURRENT.

By M.H. MOISSAN.

In a former memoir[1] we showed that it was possible to decompose anhydrous hydrofluoric acid by the action of an electric current. At the negative pole hydrogen collects; at the positive pole a gaseous body is disengaged, having novel properties. The experiment was performed in a platinum U tube, closed by stoppers of fluorite, and having at the upper part of each branch a small delivery tube, also of platinum. Through the stopper passes a platinum rod, which acts as electrode. The metal employed for the positive pole is an alloy containing 10 per cent. of iridium.

[Footnote 1: Comptes Rendus, vol. cii., p. 1543, and Chemical News, vol. liv., p. 36.]

To obtain pure anhydrous hydrofluoric acid, we begin by preparing fluorhydrate of fluoride of potassium, taking all the precautions pointed out by M. Fremy. When the salt is obtained pure, it is dried on a water bath at 100 deg., and the platinum capsule containing it is then placed in a vacuum in the presence of concentrated sulphuric acid, and two or three sticks of potash fused in a silver crucible. The acid and potash are renewed every morning for a fortnight, and the vacuum is kept at 2 cm. of mercury. Care must be taken during this desiccation to pulverize the salt every day in an iron mortar, so as to renew the surface. When the fluorhydrate contains no more water it falls to powder, and is then fit to serve for the preparation of fluoric acid; the fluorhydrate of fluoride of potassium, if well prepared, is much less deliquescent than the fluoride.

When the fluoride is quite dry, it is quickly introduced into a platinum alembic, which has just been dried by heating it to redness. The whole is kept at a gentle temperature for an hour or an hour and a half, so as to allow the decomposition to commence very slowly; the first portions of acid which come over are rejected as they carry with them traces of water remaining in the salt. The platinum receiver is then attached, and the heat increased, allowing the decomposition to proceed with a certain degree of slowness. The receiver is then surrounded with a mixture of ice and salt, and from this moment all the hydrofluoric acid is condensed as a limpid liquid, boiling at 19.5 deg., very hygroscopic, and, as is well known, giving abundant fumes in presence of the atmospheric moisture.

During this operation the platinum U tube, dried with the greatest care, has been fixed with a cork in a cylindrical glass vessel surrounded with chloride of methyl. Up to the moment of introducing the hydrofluoric acid, the leading tubes are attached to drying tubes containing fused caustic potash. To introduce the hydrochloric acid into the apparatus, it may be absorbed through one of the lateral tubes in the receiver in which it is condensed.

In some experiments we have directly condensed the hydrofluoric acid in the U tube surrounded with chloride of methyl; but in this case care must be taken that the tubes are not clogged up by small quantities of fluoride carried over, which would infallibly lead to an explosion and projections, which are always dangerous with so corrosive a liquid.

When we have introduced in advance in the small platinum apparatus a determined amount of hydrofluoric acid cooled with chloride of methyl, in tranquil ebullition at a temperature of -23 deg., the current of 20 cells of Bunsen large size, arranged in series, is passed through by means of the electrodes. An amperemeter in the circuit admits of the intensity of the current being observed.

If the hydrofluoric acid contains a small quantity of water, either by accident or design, there is always disengaged at the positive pole ozone, which has no action on crystallized silicium. In proportion as the water contained in the acid is thus decomposed, it is seen by the amperemeter that the conductivity of the liquid rapidly decreases. With absolutely anhydrous hydrofluoric acid the current will no longer pass. In many of our experiments we have succeeded in obtaining an acid so anhydrous that a current of 25 amperes was entirely arrested.

To render the liquid conducting, we have added before each experiment a small quantity of dried and fused fluorhydrate of fluoride of potassium. In this case, decomposition proceeds in a continuous manner; we obtain at the negative pole hydrogen, and at the positive pole a regular disengagement of a colorless gas in which crystallized silicium in the cold burns with great brilliancy, becoming fluoride of silicium. This latter gas has been collected over mercury, and accurately characterized.

Deville's adamantine boron burns in the same manner, but with more difficulty, becoming fluoride or boron. The small quantity of carbon and aluminum which it contains impedes the combination. Arsenic and antimony in powder combine with this gaseous body with incandescence. Sulphur takes fire in it, and iodine combines with a pale flame, losing its color. We have already remarked that it decomposes cold water, producing ozone and hydrofluoric acid.

The metals are attacked with much less energy. This is due, we think, to the small quantity of metallic fluoride formed preventing the action being very deep. Iron and manganese in powder, slightly heated, burn with sparks. Organic bodies are violently attacked. A piece of cork placed near the end of the platinum tube, where the gas is evolved, immediately carbonizes and inflames. Alcohol, ether, benzol, spirit of turpentine, and petroleum take fire on contact.

The gas evolved at the negative pole is hydrogen, burning with a pale flame, and producing none of these reactions.

When the experiment has lasted several hours, and there is not enough hydrofluoric acid left at the bottom of the tube to separate the two gases, they recombine in the apparatus in the cold, with violent detonation.

We have satisfied ourselves, by direct experiment, that a mixture of ozone and hydrofluoric acid produces none of the reactions described above.

It is the same with gaseous hydrofluoric acid. Finally we may add that the hydrofluoric acid employed, as well as the hydrofluorate of fluoride, were absolutely free from chlorine.

The gas obtained in our experiments is therefore either fluorine or a perfluoride of hydrogen.

New experiments are necessary to settle this last point. We hope soon to lay the results before the Academy.—Comptes Mendus, vol. ciii., p. 202, July 19, 1886; Chem. News.

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COHESION AND COHESION FIGURES.[1]

[Footnote 1: Notes from a lecture given to the Halifax Scientific Society, July 19, 1886.]

By WILLIAM ACKROYD, F.I.C.

1. A Law of Solubility.

It is customary to regard cohesion as the force which binds together molecules of the same substance, and in virtue of which the particles of solids and liquids are kept together, and also to speak of the attraction exerted between particles of two different bodies as adhesion. The distinction between cohesion and adhesion is a conventional one. The similarity, if not identity, of the two forces is demonstrated by the fact that while cohesion is exerted between particles of the same body, adhesion is exerted with most force between particles of allied bodies. Generally speaking, organic bodies require organic solvents; inorganic bodies, inorganic solvents. For example, common salt is highly soluble in water, but not in ether, and many fats are soluble in ether, but not in water. So many cases like these will suggest themselves to the chemist that I am justified in making the following generalization: A body will dissolve in a solvent to which it is allied more readily than in one to which it in highly dissimilar. Exceptions to the law undoubtedly exist, but none so striking as the following in support of it, viz., that the metal mercury is the only known true solvent for many metals at the normal temperature.

2. Its Connection with Mendeleeff's Periodic Law.

From this standpoint the whole subject of solution is deserving of fresh attention, as it appears highly probable that, just as Prof. Carnelley has shown by the use of my meta-chromatic scale, the colors of chemical compounds come under definite laws, which he has discovered and formulated in connection with Mendeleeff and Newlaud's periodic law,[2] so, likewise, may the solubility of an allied group of compounds, in regard to any given solvent under constant conditions of temperature, conform to similar laws; that, e.g., the chlorides of H, Na, Cu, and Ag, in Mendeleeff's Group I., may vary in their solubility in water from an extreme of high solubility in the case of hydrogen chloride to the opposite extreme of comparative insolubility in the case of silver chloride. In this natural series of compounds, hydrogen chloride is the body nearest akin to water, and silver chloride the most remote in kinship.

[Footnote 2: Philosophical Magazine, August, 1884.]

3. A Solidified Vortex Ring.

It is in virtue of cohesion that a freely suspended drop of liquid assumes the spherical form. If such a sphere be dropped on to the surface of a liquid of higher specific gravity at rest, one obtains what is called the cohesion figure of the substance of the drop. A drop of oil, e.g., spreads out on the surface of water until it is a circular thin film of concentric rings of different degrees of thickness, each displaying the characteristic colors of thin plates. The tenuity of the film increases; its cohesion is overcome; lakelets are formed, and they merge into each other. The disintegrated portions of the film now thicken, the colors vanish, and only islets of oil remain. Some liquid drops of the same or higher sp. gr. than water do not spread out in this fashion, but descend below the surface of the liquid, and, in descending, assume a ring shape, which gradually spreads out and breaks up into lesser rings. Such figures have been termed submergence cohesion figures; they are vortex rings. I have solidified such vortex rings in their first stage of formation. If drops of melted sulphur, at a temperature above that of the viscous state, be let fall into water, the drops will be solidified in the effort to form the ring, and the circular button, thick in the rim and thin in the center, may be regarded as a solidified vortex ring of plastic sulphur.

4. That a Submergence Cohesion Figure is a Vortex Ring.

It may be shown that the conditions of the formation of a submergence cohesion figure are those which exist in the formation of an aerial vortex. Those conditions in their greatest perfection are (1) a spherical envelope of a different nature from the medium in which the rings are produced; (2) a circular orifice opening into the medium; and (3) a percussive impact on the part of the sphere opposite the orifice. In the production of vortex rings of phosphorus pentoxide in the making of phosphoreted hydrogen, the spherical envelope is water, the orifice the portion of the bubble which opens into the air immediately it rises to the surface, and the impact is furnished by gravity. So, also, in the case of a submergence cohesion figure, the spherical envelope is the air surrounding the drop, the orifice the portion of it which first comes in contact with the liquid at rest; and here again the impact is due to gravity more directly than in the former case. These conditions are somewhat imperfectly copied in the ordinary vortex box, which is usually cubical in form, with a circular orifice in one side, and a covering of canvas on the opposite one, which is hit with the fist.

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[AMERICAN CHEMICAL JOURNAL.]



THE DETERMINATION OF NITRIC ACID BY THE ABSORPTION OF NITRIC OXIDE IN A STANDARD SOLUTION OF PERMANGANATE OF POTASSIUM.

By H.N. MORSE and A.F. LINN.

The method which we propose consists in the conversion of the nitric acid into nitric oxide; the absorption of the latter in a measured, but excessive, quantity of a standard solution of permanganate of potassium; and the subsequent determination of the excess of the permanganate by means of a standard solution of oxalic acid or sulphate of manganese.

THE APPARATUS.

A is an apparatus for the generation of carbon dioxide free from air, which will be explained hereafter.

B is a flask, having a capacity of 125 or 150 c.c., in which the nitrate is decomposed in the usual manner by means of ferrous chloride and hydrochloric acid.

C is a small tube for the condensation of the aqueous hydrochloric acid which distills over from B.

D is a Geissler bulb, containing a concentrated solution of potassium carbonate, to arrest any acid vapors coming from C.

E, E are two pieces of ordinary combustion tubing, having a length of about 650 or 700 mm., in which is placed the permanganate solution employed for the absorption of the nitric oxide. Their open ends are provided with lips in order to facilitate the pouring of liquids from them, care being taken not to so distort the ends that rubber stoppers cannot be made to fit them tightly. They are placed in a nearly horizontal position in order to diminish the pressure required to force the gases through the apparatus and thus lessen the danger of leakage through the rubber joints.

a is a tube through which the ferrous chloride and hydrochloric acid are introduced into B, as in the method of Tiemann-Schulze.

b serves for the introduction of carbon dioxide to expel the air before the decomposition of the nitrate, and the nitric oxide afterward.

c is an unbroken tube ending at the lower surface of the stopper in B, and at the bottom of C.

The rubber joint, d, is furnished with a Mohr and also a screw pinch cock. The joints, e and f, are furnished with Mohr pinch cocks. The rubber tubing upon these should be of the best quality, and must be carefully tied.



THE SOLUTIONS.

In consequence of the large volume of the permanganate solution required for the complete absorption of the nitric oxide, we have found it advantageous to use three solutions instead of two.

1. A solution of permanganate such that one c.c. is equivalent to about fifteen milligrammes of nitrate of potassium, according to the reaction:

KMnO_{4} + NO = KNO_{3} + MnO_{2}.

This solution is employed for the absorption of the nitric oxide. Its strength need not be exactly known. There is no objection to a more concentrated solution, except that which pertains to all strong standard solutions, namely, that a small error in measurement would then give a larger error in the results. 100 c.c. of this solution are required for each determination, and the measurement is always made in one and the same 100 c.c. measuring flask, which, if necessary, should be labeled to distinguish it from that used for solution No. 2.

2. A solution of oxalic acid which is very slightly stronger than that of the permanganate just described—that is, a solution such that one c.c. of it will somewhat more than decompose one c.c. of the permanganate, according to the reaction:

2KMnO{4} + 3H{2}SO{4} + 5C{2}H{2}O{4}.2H{2}O = K{2}SO{4} + 2MnSO{4} + 18H{2}O + 10CO{2}.

The exact strength of this solution need not be known, since we only require the difference in value between it and solution No. 1, which is determined by means of solution No. 3. 100 c.c. of this solution are also required for each determination, and the measurement, as in the preceding case, is always made in the same 100 c.c. measuring flask.

3. A dilute, carefully standardized solution of permanganate of potassium.

The method of using these solutions is as follows: 100 c.c. of No. 1 and No. 2 are measured off (each solution in its own measuring flask), brought together in a covered beaker glass, and acidified with dilute sulphuric acid. The excess of oxalic acid is then determined by means of solution No. 3.

When it is desired to make a determination of nitric acid, 100 c.c. of solution No. 1 are measured off, and as much of it as may be convenient is poured into the tubes, E, E, together with about a gramme of zinc sulphate for each tube, which substance appears to considerably facilitate the absorption of the nitric oxide by the permanganate. When the operation is over, the contents of E, E are poured into a beaker glass. 100 c.c. of solution No. 2 are then measured off, and a portion, together with a little sulphuric acid, poured into E, E, to dissolve the oxide of manganese which has separated during the absorption of the nitric oxide. The oxide having been dissolved, the liquid in E, E, and the rinsings of the tubes, also the residues of permanganate and oxalic acid left in the measuring flasks, and the rinsings from these, are all brought together in the same beaker glass. Finally, the amount of solution No. 3 required to decompose the excess of oxalic acid is determined. If we subtract from the amount thus found the quantity of permanganate required to equalize solutions Nos. 1 and 2 (previously ascertained), we shall have the amount of permanganate actually reduced by the nitric oxide, according to the reaction:

6KMnO{4} + 10NO = 3K{2}O + 6MnO + 5N{2}O{5};

in other words, on the basis that one molecule of potassium permanganate will oxidize one and two-thirds molecules of nitric oxide:

(KMnO_{4} = 1-2/3 NO).

The method of using the apparatus is simple. The nitrate is placed in B, and the joints made tight, except that at f, which is left open. A current of carbon dioxide is passed through the apparatus until all of the air has been displaced. Connection is then made at f, and soon afterward the current of carbon dioxide is shut off at d.

The flask, B, is now heated as long as may be necessary in order to produce, on cooling, the diminished pressure required for the introduction of the ferrous chloride and hydrochloric acid. Before removing the flame, the joint at f is closed to prevent the return of the permanganate solution.

As soon as the flask, B, has become sufficiently cool, the ferrous chloride and hydrochloric acid are introduced through the tube, a (which has been full of water from the first), in the same manner and quantities as in the well-known Tiemann-Schulze method.

The pinch cock at d is then opened, and the apparatus allowed to fill with carbon dioxide. When the pressure has become sufficient to force the gas through the solution of permanganate, the pinch cock at f is removed. It should be opened only slightly and with great caution at first, unless one is certain that the pressure is sufficient. If the pressure is insufficient, the fact will be made apparent by a rise of the permanganate in the small internal tube.

The flow of carbon dioxide is now reduced to a very slow current, or entirely cut off. The contents of B are slowly heated, until the decomposition of the nitrate is complete and the greater part of the nitric oxide has been expelled, when the apparatus is again closed at f and d, and allowed to cool. The tube, a, is then washed out, by the introduction through it into B of a few cubic centimeters of strong hydrochloric acid.

The process of filling the apparatus with carbon dioxide, and of heating the contents of B, is repeated. When it becomes apparent, from the light color of the liquid in B, that all of the nitric oxide has been expelled from it, the current of carbon dioxide is increased and the heating discontinued. Care must be taken, however, not to admit too strong a current of carbon dioxide, lest some of the nitric oxide should be forced unabsorbed through the permanganate solution. It is also necessary, for the same reason, to avoid too rapid heating during the decomposition of the nitrate.

When all of the nitric oxide has been forced into the solution of permanganate, the determination is made in the manner already described.

To test the method, nine determinations were made with quantities of pure nitrate of potassium varying from 100 to 200 milligrammes. The maximum difference between the volumes of permanganate actually used and those calculated was 0.05 c.c., while the main difference was 0.036 c.c. The measurements of the permanganate were made from a burette which had been carefully calibrated. We also made a number of determinations, using a solution of manganous sulphate in the place of the oxalic acid. The advantage of this method lies in the fact that it is not necessary to dissolve the oxide which is precipitated upon the glass within the tubes, E, E, since, in the presence of an excess of permanganate, the reduction by nitric oxide extends only to the formation of MnO_{2}; also in the fact that the solution of manganous sulphate is more stable than that of oxalic acid. A solution of the sulphate having been once carefully standardized, can be used for a long time to determine the value of permanganate solutions.

The details of the method are as follows: A solution of manganous sulphate slightly stronger than No. 1 is prepared.

The difference between 100 c.c. of it and 100 c.c. of No. 1 is ascertained, according to the method of Volhard, by means of solution No. 3.

The contents of E, E, together with the rinsings from the tubes, are poured into a capacious flask. 100 c.c. of the manganous sulphate and a few drops of nitric acid are then added, and the whole boiled. Finally, the excess of manganous sulphate is determined, in the manner described by Volhard, by means of solution No. 3. Subtracting from the total amount of permanganate thus used the quantity required to equalize the 100 c.c. of solution No. 1 and the 100 c.c. of the manganous sulphate, we shall have the quantity of permanganate reduced by the nitric oxide.

It must, however, be remembered that the value of solution No. 3 is now to be calculated on the basis of the equation KMnO_{2} + NO = KNO_{3} + MnO_{2}. One molecule of permanganate equals one molecule of nitric oxide when manganous sulphate is used, since no part of the permanganate employed in this method is reduced below the superoxide condition. In other words, solution No. 3 now represents only three-fifths as much nitric acid as it does when oxalic acid is used.

The results obtained by this method were moderately satisfactory, but not quite so exact as those obtained when oxalic acid was used. A series of four determinations gave differences, between the volumes of permanganate calculated and used, of 0.05 to 0.15 c.c.

The principal objection to the method lies in the difficulty of determining, in the presence of the brown oxide of manganese, the exact point at which the oxidation is complete.

The carbon dioxide generator, A, was devised by us to take the place of the ordinary generators, in which marble is used. We have found that a submersion of twenty hours in boiling water does not suffice to completely remove the air which, as is well known, is contained in ordinary marble; hence some other substance must be employed as a source of the gas. In the apparatus which we are about to describe, the acid carbonate of sodium is used.

It consists of a long, narrow cylinder (450 x 60 mm.); a tightly fitting rubber stopper, through which three tubes pass, as shown in the figure; a small cylinder, F, containing mercury; and a sulphuric acid reservoir, G.

The tube, g, is drawn out to a fine point at the end and curved, so that the acid which is delivered into A falls upon and runs down the outside of the tube. The tube, h, dips under the mercury in F. G and g are connected by means of a long piece of rubber tubing which is supplied with a screw pinch cock.

The apparatus is made to give any required pressure by raising or lowering G and F; but the elevation of G, as compared with that of F, should always be such that the gas will force its way through h rather than g. The upper part of the cylinder, F, is filled with cotton wool to prevent loss of mercury by spattering.

The material placed in A consists of a saturated solution of acid carbonate of sodium, to which an excess of the solid salt has been added. The sulphuric acid is the ordinary dilute. The apparatus, if properly regulated, serves its purpose very well. The principal precaution to be observed in using it is to avoid a too sudden relieving of the pressure, which would, of course, result in the introduction of an unnecessarily large quantity of sulphuric acid into A.

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WATER OF CRYSTALLIZATION.

By W.W.J. NICOL, M.A., D.Sc.

When a hydrated salt is dissolved, does it retain its water of crystallization, or does this latter cease to be distinguishable from the solvent water? Both views have found advocates among chemists who have looked at the question of solution, and both have been supported by arguments more or less to the point. But among the possible means of solving this question there is one which has entirely escaped the notice of those interested in the subject. And those who hold that water of crystallization exists in solution have been entirely oblivious of the fact that, while they are ready to accept the results of the modern science of thermo-chemistry, and to employ them to support their views on hydration, yet these very results, if correct, prove without a shadow of a doubt that water of crystallization does not exist in solution.

The proof is so clear and self-evident when once one's attention is directed to it, that, though I intend to develop it more fully on another occasion, I feel that it is better to publish an outline of it at once.

Thomsen has found that the heat of neutralization of the soluble bases of the alkalies and alkaline earths with sulphuric acid has a mean value of 31.150 c. within very narrow limits. When hydrochloric or nitric acid is employed, the value is 27.640 c., also within very narrow limits. Now, this agreement of the six bases in their behavior with sulphuric acid, much more of the seven bases with both HNO_{3} and HCl, is so close that it cannot be regarded as accidental, but, in the words of Meyer, the heat of formation of a salt in aqueous solution is a quantity made up of two parts, one a constant for the base, the other for the acid. But of the twenty salts thus formed, some are anhydrous in the solid state, others have water of crystallization, up to ten molecules in the case of Na_{2}SO_{4}. If water of crystallization exists in solution, it will be necessary to suppose that this agreement is accidental, which is absurd, as a glance at the probabilities will show. Thomsen himself expressly states that he regards the dissolved state as one in which the conditions are comparable for all substances; this would be impossible if water of crystallization were present.

A still stronger proof is afforded by the "avidity" of Thomsen or the "affinity" of Ostwald; both have worked on the subject, taking no account of water of crystallization, and the results, e.g., for H{2}SO{4} and HCl with NaHO, where water of crystallization may come in, are entirely confirmed by Ostwald's results on inversion and etherification, where there can be no water of crystallization.

The proof is complete, water of crystallization cannot be attached to the salt in solution, or if it is, no heat is evolved on union more than with solvent water. The alternative is to suppose that the whole of the above thermo-chemical results are coincidences.

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ALPINE FLOWERS IN THE PYRENEES.

Bagneres De Luchon, in the department of the Haute Garonne, is a gay town of some 5,000 inhabitants. A friend told me that he once suffered so much from the heat there in June, that he determined never to go to the Pyrenees again. We were there the second week in June, and we suffered more from rain and cold, and were very glad of a fire in the evening.

Except to the south, in the direction of the Porte de Venasque, one of the chief mule passes into Spain during summer, where there are fine snow-capped mountains, the scenery from the town is not grand, but it is within easy reach of the wildest parts of the Pyrenees.

It is the nearest town to the Maladetta, their highest point, in which the Garonne rises, and among whose rocks is one of the last strongholds of the ibex or bouquetin, the "wild goat" mentioned by Homer. Eagles and vultures are to be seen sailing about the sky near Luchon nearly every day, and bears, which in the Pyrenees are neither mythical nor formidable, descend to within a few miles of the town after wild strawberries, which abound there.

We heard of two female peasants lately gathering wild strawberries who were suddenly confronted with competitors for the spoil in the shape of a she bear and two cubs. It was doubtful whether man or beast was the more surprised. The cubs began to growl, but their dam gave both of them a box on the ears for their bad manners, and led them away. As for flowers, the neighborhood of Luchon has the reputation, perhaps not undeserved, of being the most flowery part of the Pyrenees.

We went the usual expeditions from the town, in spite of the weather, and I will try to remember what plants we noticed in each of them. The first trip was to the Vallee du Lys. In spite of the spelling, the name suggests lilies of the valley, but we are told that lys is an old word meaning water, and that the valley took its name from the number of cataracts, not from lilies, there.

However this may be, a lily grows there in great profusion, and was just coming into flower toward the middle of June. It is the Lis de St. Bruno (Anthericum liliastrum), a plant worthy of giving its name to a valley of which it is a characteristic feature. Still more conspicuous at the time when we were there were the Narcissus poeticus, abundant all round Luchon, but already past in the low meadows near the town, but higher up, at an elevation of about 4,000 ft., it was quite at its best, and whitened the ground over many acres.

I looked about for varieties, but failed to detect any special character by which it could be referred to any of the varietal names given in catalogues, and concluded that it was N. poeticus pure and simple. Pulmonarias were abundant along the road, as also in the whole region of the Pyrenees, the character of the leaves varying greatly, some being spotless, some full of irregular white patches, others with well defined round spots. They varied, too, from broad heart-shaped to narrow lanceolate, and I soon concluded that it was hopeless to attempt any division of the class founded upon the leaves.

Besides the beautiful flowers of Scabious mentioned before, a new feature in the meadows here was the abundance of Astrantia major. A pure white Hesperis matronalis was also common, but I saw no purple forms of it. Geranium phaeum also grew everywhere in the fields, the color of the flower varying a good deal. Hepaticas were not so common by the roadside here as at Eaux Bonnes, but are generally distributed. Many of them have their leaves beautifully marbled, and I selected and brought away a few of the best, in hopes that they may keep this character. I was struck everywhere by the one-crowned appearance of the Hepaticas, as if in their second year from seed.

On the mountains, where they were still in flower, I did not find the colors mixed, but on one mountain they would be all white, on another all blue. I do not recollect to have seen any pink. Meconopsis cambrica is common in the Pyrenees. I observe that in Grenier's "French Flora" the color of the flower is given as "jaune orange," but I never saw it either in England or in France with orange flowers till I saw it covering a bank by the side of the road to the Vallee du Lys. I was too much struck by it to delay securing a plant or two, which was lucky, for when we returned every flower had been gathered by some rival admirers.

Another expedition from Luchon is to the Lac d'Oo. This, too, is famous for flowers; but especially so is a high valley called Val d'Esquierry, 2,000 ft. or 3,000 ft. above the village d'Oo, at which the carriage road ends. Botanists call this the garden of the Pyrenees, and, of course, I was most anxious to see it.

The landlord of our hotel was quite enthusiastic in his description of the treat in store for me, enumerating a long catalogue of colors, and indicating with his hand, palm downward, the height from the ground at which I was to expect to see each color. I was afterward told that he had never been to the famous valley, being by no means addicted to climbing mountains.

During the first part of the drive from Luchon we saw hanging from the rocks by the roadside large masses of Saponaria ocymoides, varying much in the shade of color of the flowers. This is a plant which I find it better to grow from cuttings than from seed. The best shades of color are in this way preserved, and the plants are more flowery and less straggling. As we got near the end of the carriage road, the meadows became more crowded with flowers known in England only in gardens.

Besides such plants as Geranium pyrenaicum growing everywhere on the banks, the fields were full of a light purple geranium—I think sylvaticum. Here, too, I noticed Meconopsis cambrica with orange flowers. Narcissus poeticus was also there, and so were some splendid thistles, large and rich in color. But the most remarkable part of the coloring in the meadows was produced by different shades of Viola cornuta carpeting the ground. We noticed this plant in many parts of the Pyrenees, but here especially.

From the end of the road I started with a guide for the promised garden of the Val d'Esquierry. By the side of the steep and winding path I noticed Ramondia pyrenaica—the only place I saw it in the Luchon district. Other notable plants were a quantity of Anemone alpina of dwarf growth and very large flowers, covering a green knoll near a stream. A little beyond, Aster alpinus was in flower, of a bright color, which I can never get it to show in gardens. These, with the exception of a few saxifrages and daffodils of the variety muticus, were about the last flowers I saw there.



Promise of flowers there was in abundance. Aconites, I suppose napellus, and also that form of A. lycoctonum with the large leaves known as pyrenaicum, were just enough grown to recognize. The large white Asphodel, called by French botanists A. albus, but better known in gardens as A. ramosus, which grows everywhere in the Pyrenees, and the coarse shoots of Gentiana lutea were just showing.

Further on the daffodils were only just putting their noses through the yellow dead grass, which the snow had hardly left and was again beginning to whiten, for the rain, which had been coming down in torrents ever since I left the carriage and had wet me through, had now changed to snow. Still I went on, in spite of the bitter cold, hoping that I should come to some hyperborean region where the flowers would be all bright; but my guide at last undeceived me, and convinced me that we were far too early, so we went down again, wiser and sadder, and I advise my friends who wish to see the Val d'Esquierry in its beauty not to visit it before July at the earliest.

I have still one mountain walk to describe, a far more successful one, but it must be deferred till another week.—C. Wolley Dod, in the Garden.

* * * * *

Turtle shells may be softened by hot water, and if compressed in this state by screws in iron or brass moulds, may be bent into any shape, the moulds being then plunged into cold water.

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A CENTURY PLANT IN BLOOM.

A huge agave, or century plant, is now blooming at Auburn, N.Y. A few days ago the great plant became tinged with a delicate yellowish-white color, as its 4,000 buds began to develop into the full-blown flowers, whose penetrating fragrance, not unlike that of the pond lily, now attracts swarms of bees and other insects. The plant was purchased in 1837 by the owner, and was then twelve years old. For half a century the agave has lain around his greenhouses in company with several others, and no special care has been taken of it, except to protect it somehow in winter, that it might be fresh for the next summer's growth. The plant has always been a hardy specimen, and required little care. Its whole life, now speedily approaching a termination in the fulfillment of the end of its existence—flowering—has been a sluggish course. Its growth has been steady and its development gradual. Occasionally it has thrust out a spiked leaf until, in size, it became greater than its fellow plants and took on the likeness of an enormous cabbage which had been arrested in its development and failed to attain perfection. Early last April its appearance began to undergo a decided change. Its resemblance to a cabbage lessened, and it began to look like a giant asparagus plant. On April 12, the great fleshy leaves, massed together so as to impress the imprint of their spines upon one another, began to unfold, and a thick, succulent bud burst up amid the leaves. Slowly the stalk developed from the bud and assumed gigantic proportions. Green scales appeared in regular arrangement about the stalk, marking the points from which lateral branches were to spring. The thick stalk, tender and brittle at first as new asparagus, became tough and hard enough to resist a knife, and its surface assumed the gritty character of the leaves of the plant. The low roof of the hothouse became an obstruction to further growth, and had to be removed. Lateral limbs were, at a later period, thrust out in great numbers, each of them bearing small branches, as do strawberry plants, on which hang sprays of buds in bunches of from three to ten, making in all many hundreds, all waiting for the completion and blooming of the topmost buds. The inflorescence of the century plant is peculiar, and the appearance of flowers on the lower branches may be simultaneous with, or consecutive to, the blossoming on the upper limbs. With the appearance of the lateral outshoots the great aloe lost its likeness to asparagus, and at present bears resemblance to an immense candelabra. The plant is now fully matured, and has a height of twenty-seven feet. There are thirty-three branches on the main stem, and, by actual count, one of the lateral limbs was found to bear 273 perfect buds, some of whose green sepals have spread, revealing the yellowish-white petals and essential parts of the plant. The ample panicles crowded with curious blossoms are, as, indeed, the Greek name of the plant—agave—signifies, wonderful.

There is a pathetic view to be taken of the great plant's present condition. For years it has been preparing to flower, and the shoot it has sent up is the dying effort. The blossoms carry in them the life of new plants, and the old plant dies in giving them birth. It is commonly supposed that this plant, the Agave Americana, or American aloe, blooms only at the end of 100 years, hence the common name century plant.

Only two plants are on record among the floriculturists as having bloomed in New York State. Thirty years ago, a century plant, of which the Casey aloe was a slip, flowered in the greenhouses of the Van Rensselaer family at Albany. In 1869, a second plant blossomed at Rochester. At present, two aloes, one at Albany, the other at Brooklyn, are reported as giving evidences of approaching maturity. They are pronounced not American aloes, or century plants, but Agave Virginica, a plant of the same family commonly found in sterile soil from Virginia to Illinois and south, and blossoming much more frequently. In Mexico the century plant is turned to practical account and made a profitable investment to its owners. After the scape has reached its full growth it is hewn down, and the sap, which fills the hollow at its base, is ladled out and converted by fermentation into "agave wine," or "pulque," the favorite drink of the Mexicans. This pulque, or octli, has an acid resembling that of cider, and a very disagreeable odor, but the taste is cooling and refreshing. A brandy distilled from pulque is called "aquardiente," or "mexical." The plant, by tapping, can be made to yield a quart of sap daily. The fibers of the leaves when dried furnish a coarse thread known as Pita flax, and when green are used in Mexico as fodder for cattle. Razor strops or hones are also made from the leaves, which contain an abundance of silica and give rise to a very sharp edge on a knife applied with friction across the surface of the dried leaf.

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CREOSOTE A SPECIFIC FOR ERYSIPELAS.

Time was when the advocate of a specific was laughed at by the scientific world, but since it is known that so many forms of disease are the direct result of some kind of germ life, it is no longer a misnomer to call a medicine which will certainly and always destroy the germ which produces so many forms of disease a specific.

In the light of this definition, founded upon the experience of forty years' successful practice in treating this form of disease with creosote, the writer is prepared to indorse the heading of this article. Having used all the different remedies ordinarily prescribed, they have long since been laid aside, and this one used in all forms of the disease exclusively, and with uniform success.

In 1863 it was the writer's fortune to spend several weeks in a military hospital in Memphis as a volunteer surgeon, under the direction of Dr. Lord. In conversation with him, the use of this article was mentioned, which appeared new to him, and a case was put under treatment with it, with such prompt favorable results as to elicit his hearty commendation, and, at his suggestion, Surgeon-General Hammond was informed of it.

All injuries, of whatever kind, have been treated with dressings of this remedy, and where this has been done from the first to last, in no instance has there been an attack of erysipelas.

The usual manner of application was in solution of six to twenty drops to the ounce of water, keeping the parts covered with cloths constantly wet with it. In ulcers or wounds it may be used in the form of a poultice, by stirring ground elm into the solution, the strength to be regulated according to the virulence of the attack. Ordinarily, ten drops to the ounce is strong enough for the cutaneous form of the disease and in dressings for wounds or recent injuries. If the inflammation threatens to spread rapidly, it should be increased to twenty or more drops to the ounce of water.

The antiseptic properties of this remedy render it of additional value, as it will certainly destroy the tendency to unhealthy suppuration, and thus prevent septicaemia.

In the treatment of hundreds of cases of erysipelas but one fatal case has occurred, and that one in an old and depraved system. In the less violent attacks no other remedy was used, but where constitutional treatment was indicated, the usual appropriate tonics were prescribed.

There is no question in my mind but that creosote is as much a specific in erysipelas as quinine is in intermittent fever, and may be used with as much confidence.—St. Louis Med. Jour.

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A NEW APPARATUS FOR THE STUDY OF CARDIAC DRUGS.

By WILLIAM GILMAN THOMPSON, M.D., New York.

The apparatus was devised by Mr. R.D. Gray (the inventor of the ingenious "vest camera" and other photographic improvements) and by myself. I described what was required and suggested various modifications and improvements, but the mechanical details were worked out exclusively by him. To test the rapidity of the camera, we photographed a "horse-timer" clock, with a dial marking quarter seconds, and succeeded in taking five distinct photographs in half a second with one lens, which has never before been accomplished excepting by Professor Marey,[1] at the College de France, who has taken successive views of flying birds, falling balls, etc., with one lens at a very rapid rate. His camera was unknown to me until after mine was constructed, so that as a success in photography alone the work is interesting.

[Footnote 1: La Methode Graphique (Supplement), Paris, 1885.]

The camera consists of a circular brass box, 51/2 inches in diameter and 11/4 inches deep, containing a circular vulcanite shutter with two apertures, behind which is placed a circular dry plate. Both plate and shutter are revolved in opposite directions to each other by a simple arrangement of four cogged wheels moved by a single crank. The box is perforated at one side by a circular opening, 13/4 inches in diameter, from the margin of which projects at a right angle a long brass tube (Fig. 1), which carries the lens. In Fig. 2 the lid of the box has been removed, and the bottom of the box, with the wheels, springs, and partially closed shutter, is presented. The lid is double—that is, it is a flat box in itself. It contains nothing but the dry plate, supported at its center upon a small brass disk, against which disk it is firmly pressed by a pivot attached to a spring fastened in the lid. The aperture in one side of this double lid, which corresponds with that seen in the floor of the box, may be closed by a slide, so that the lid containing the plate can be removed like an ordinary plate holder and carried to a dark room, where it is opened and the plate is changed. When the lid is replaced this slide is removed, and as the shutter is made to revolve, the light falls upon whatever portion of the dry plate happens to be opposite the opening.

By reference to Fig. 2, it will be seen that when the large wheel which projects outside of the box is revolved by a crank, it turns the small ratchet wheel, which bears an eccentric pawl. (The crank has been removed in Fig. 2; it is seen in Fig. 1.) The central wheel has only six cogs. The pawl is pressed into one of these cogs by a spring. It pushes the central wheel around one-sixth of its circumference, when it returns to be pressed into the next cog. While the pawl returns, it necessarily leaves the central wheel at rest, and whatever momentum this wheel carries is checked by a simple stop pressed by a spring upon the opposite side. The central wheel carries a square axle, which projects through a small hole in the center of the double lid and fits into the brass disk before alluded to, causing the disk to revolve with the axle. The disk is covered by rubber cloth; and as the dry plate is pressed firmly against the rubber surface by the spring in the lid, the plate adheres to the rubber and revolves with the disk. Thus every complete revolution of the central wheel in the floor of the box carries with it the dry plate, stops it, and moves it on again six times. The velocity of revolution of the plate is only limited by the rapidity with which one can turn the crank.

The shutter is revolved in the opposite direction by a wheel whose cogs are seen fitting into those of the little wheel carrying the eccentric pawl.



The two apertures in the shutter are so placed that at the instant of exposure of the plate it is momentarily at rest, while the plate when moving is covered by the shutters. This arrangement prevents vibration of the plate and blurring of the image. The camera is mounted by two lateral axles with screw clamps upon two iron stands, such as are in common use in chemical laboratories. A brass rod attached to the tube steadies it, and allows it to be screwed fast at any angle corresponding to the angle at which the heart is placed. It is thus easy to put a manometer tube in the femoral artery of an animal, bend it up alongside of the exposed heart, and simultaneously photograph the cardiac contraction and the degree of rise of the fluid in the manometer(!). The tube is arranged like the draw tube of a microscope. It is made long, so as to admit of taking small hearts at life-size. The stand carries a support for the frog or other animal to be experimented upon, and a bottle of physiological salt solution kept warm by a spirit lamp beneath.



The whole apparatus is readily packed in a small space. I have already taken a number of photographs of various hearts and intestines with it, and the contraction of the heart of the frog produced by Strophanthus hispidus, the new cardiac stimulant, is seen in Fig. 3, taken by this new instrument. The apparatus has the great advantage that six photographs of a single cardiac pulsation, or of any muscular contraction, may be easily taken in less than one second, or, by simply turning the crank slower, they may be taken at any desired rate to keep pace with the rhythm of the heart. The second hand of a watch may be placed in the field of view and simultaneously photographed with the heart, so that there can be no question about the series of photographs all belonging to one pulsation.



I have already called attention[13] to the ease with which these photographs are enlarged for lecture room demonstration, either on paper or in a stereopticon, and the ease with which they may be reproduced in print to illustrate the action of drugs.

[Footnote 13: Medical Record, loc. cit.; Recent Advances in Methods of Studying the Heart, Medical Press, Buffalo, March 1, 1886, p. 234; Instantaneous Photographs of the Heart, Johns Hopkins University Circulars, March, 1886, p. 60.]

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