That many limestones are more or less charged with petroleum is well known; and in addition to those mentioned above, the Silurian limestone at Collingwood, Canada, may be cited as an example. As I have elsewhere shown, we have reason to believe that the petroleum here is indigenous, and has been derived, in part, at least, from animal organisms; but the limestones are generally compact, and if cellular, their cavities are closed, and the amount of petroleum which, under any circumstances, flows from or can be extracted from limestone rock is small. On the other hand, the bituminous shales which underlie the different oil regions afford an abundant source of supply, holding the proper relations with the reservoirs that contain the oil, and are spontaneously and constantly evolving gas and oil, as may be observed in a great number of localities. For this reason, while confessing the occurrence of petroleum and asphaltum in many limestones, I am thoroughly convinced that little or none of the petroleum of commerce is derived from them.

Prof. S.F. Peckham, who has studied the petroleum field of southern California, attributes the abundant hydrocarbon emanations in that locality to microscopic animals. It is quite possible that this is true in this and other localities, but the bituminous shales which are evidently the sources of the petroleum of Pennsylvania, Ohio, Kentucky, etc., generally contain abundant impressions of sea weeds, and indeed these are almost the only organisms which have left any traces in them. I am inclined, therefore, now, as in my report on the rock oils of Ohio, published in 1860, to ascribe the carbonaceous matter of the bituminous shales of Pennsylvania and Ohio, and hence the petroleum derived from them, to the easily decomposed cellular tissue of alg which have in their decomposition contributed a large percentage of diffused carbonaceous matter to the sediments accumulating at the bottom of the water where they grew. In a recent communication to the National Academy of Sciences, Dr. T. Sterry Hunt has proposed the theory that anthracite is the result of the decomposition of vegetable tissue when buried in porous strata like sandstone; but an examination of even a few of the important deposits of anthracite in the world will show that no such relationship as he suggests obtains.

Anthracite may and does occur in sedimentary rocks of varied character, but, so far as my observation has extended, never in quantity in sandstone. In the Lower Silurian rocks anthracite occurs, both in the Old World and in the New, where no metamorphism has affected it, and where it is simply the normal result of the long continued distillation of plant tissue; but the anthracite beds which are known and mined in so many countries are the results of the metamorphism of coal-beds of one or another age, by local outbursts of trap, or the steaming and baking of the disturbed strata in mountain chains, numerous instances of which are given on a preceding page.

M. Mendeleeff, in his article already referred to, misled by a want of knowledge of the geology of our oil-fields, and ascribing the petroleum to an inorganic cause, connects the production of oil in Pennsylvania and Caucasia with the neighboring mountain chains of the Alleghanies and the Caucasus; but in these localities a sufficient amount of organic matter can be found to supply a source for the petroleum, while the upheaval and loosening of the strata along lines parallel with the axes of elevation has favored the decomposition (spontaneous distillation) of the carbonaceous strata. It should be distinctly stated, also, that no igneous rocks are found in the vicinity of productive oil-wells, here or elsewhere, and there are no facts to sustain the view that petroleum is a volcanic product.

In the valley of the Mississippi, in Ohio, Illinois, and Kentucky, are great deposits of petroleum, far removed from any mountain chain or volcanic vent, and the cases which have been cited of the limited production of hydrocarbons in the vicinity of, and probably in connection with, volcanic centers may be explained by supposing that in these cases the petroleum is distilled from sedimentary strata containing organic matter by the proximity of melted rock, or steam.

Everything indicates that the distillation which has produced the greatest quantities of petroleum known was effected at a low temperature, and the constant escape of petroleum and carbureted hydrogen from the outcrops of bituminous shales, as well as the result of weathering on the shales, depriving them of all their carbon, shows that the distillation and complete elimination of the organic matter they contain may take place at the ordinary temperature.

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ESTIMATION OF SULPHUR IN IRON AND STEEL.

By GEORGE CRAIG.

For wellnigh two years I have been estimating sulphur in iron and steel by a modification of the evolution process, which consists in passing the evolved gases through an ammoniacal solution of peroxide of hydrogen, which oxidizes the sulphureted hydrogen to sulphuric acid, which latter is estimated as usual. The modus operandi is as follows:



100 grains of the iron or steel are placed in the 10 oz. flask, a, along with oz. water; 1 oz. hydrochloric acid are added from the stoppered funnel, b, in such quantities at a time as to produce a moderate evolution of gas through the nitrogen bulb, c, which contains 1/8 oz. (20 vols.) peroxide of hydrogen and oz. ammonia. The tube, d, is to condense the bulk of the hydrochloric acid which distills over during the operation. When all the acid has been added and the evolution of gas becomes sluggish, heat is applied and the liquid boiled till all action ceases. Air is blown through the aparatus for a few minutes and the contents of c and d washed into a small beaker and acidified with hydrochloric acid, boiled, barium chloride added, and the barium sulphate filtered off after standing a short time. A blank experiment must be done with each new lot of peroxide of hydrogen obtained, which always gives under 0.1 barium sulphate with me.

The whole operation is finished within two hours, the usual oxidation process occupying nearly two days; and the results obtained are invariably slightly higher than by the oxidation processes.

Until lately I have always added excess of chlorate of potash to the residue left in a, evaporated it nearly to dryness, diluted, filtered, and added chloride of barium to the diluted filtrate, but only once have I obtained a trace of precipitate after standing 48 hours, and the pig-iron in that case contained 8 per cent. of silicon, so that all the sulphur is evolved during the process. It has been objected to the evolution process that when the iron contains copper all the sulphur is not evolved, but theoretically it ought to be evolved whether copper is present or not; and to test the point I fused 3 lb. of ordinary Scotch pig-iron with some copper for half an hour in a Fletcher's gas furnace. No copper could be detected in the iron by mere observation with a microscope, but it gave on analysis 0.225 per cent. of copper, and on estimating the sulphur in it by the above process and by oxidation with chlorate of potash and hydrochloric acid, using 100 grains in each case, and performing blank experiments, I found:

By peroxide of hydrogen process 0.0357 per cent. By oxidation (KClO_{3} and HCl) process, 0.0302 "

so that even in highly cupriferous pig-iron all the sulphur is evolved on treatment with strong hydrochloric acid.—Chem. News.

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THE AIR IN RELATION TO HEALTH.

[Footnote: Abstract of a lecture before the Master Plumbers' Association, New York, Nov. 2. 1882.]

By Prof. C. F. CHANDLER.

It is only about one hundred years since the first important facts were discovered which threw light upon the chemistry of atmosphere. It was in 1774 that Dr. Priestley, in London, and Scheele, in Sweden, discovered the vital constituents of the atmosphere—the oxygen gas which supports life. The inert gas, nitrogen, had been discovered a year or two before. When we examine our atmosphere, we find it is composed of oxygen and nitrogen. The nitrogen constitutes no less than 80 per cent, of the atmosphere; the remaining 20 percent, consists of oxygen, so that the atmosphere consists almost entirely of these two gases, odorless and colorless and invisible. The atmosphere is, however, never free from moisture; a certain amount of aqueous vapor is always present. The quantity can hardly be stated, as it varies from day to day and month to month; it depends upon the temperature and other conditions. Then we have the gas commonly called carbonic acid in extremely minute quantities, about one part in 2,500, or four one-hundredths of one per cent. A small quantity of ammonia and a small quantity of ozone are also present.

Besides these gases which have been enumerated, and which play an important part in supporting life in both the kingdoms of nature, we find a great many solids. Every housewife knows how dust settles upon everything about the house. This dust has recently been the subject of most active study, and it proves to be quite as important as the vital oxygen that actually supports life. When we examine this dust—and it falls everywhere, not only in the city streets, but upon the tops of mountains, upon the deck of the ocean steamer, and the Arctic snow—we find some of it does not belong to the earth, and, as it is not terrestrial, we call it cosmical. And when it falls in large pieces we call it a meteorite or shooting star. When the Challenger crossed the Atlantic, and soundings were made in the deep sea, in the mud that was brought up and examined there were found various little particles that were not terrestrial. They were dust particles that were dropped into the atmosphere of the earth from outer space. Then we have terrestrial dust, and we divide that into mineral and organic. The mineral consists chiefly of clay, sand, and, near the ocean, salt. Then we have organic matter. Some of this is dead leaves which have been ground to powder. Animal matter has also become dry and reduced to powder, and we actually find the remains of animals and plants floating upon the atmosphere, especially in the city. Examinations of the dust which had collected upon the basement and higher windows of a Fifth avenue residence showed that the dust upon the basement floor was chiefly composed of sand. And the higher up I went, the smaller proportion of sand and a larger proportion of animal matter, so that the dust that blows into our faces is largely decomposing animal substance.

But we have a living matter in the atmosphere. We often notice in the summer, after a rain, that the ground is yellow. On gathering up the yellow powder and examining it under the microscope, we find that it consists of pollen. The pollen of rag weed and other plants is supposed to be the cause of hay fever. But we also have something far more important in the germs of certain classes of vegetation. The effects are familiar. If food is put away, it becomes mouldy. This mould is a peculiar kind of vegetation which is called a fungus, and the plants fungi. In order for this mould to develop a certain temperature and a certain degree of moisture are necessary. Our food, we say, decays. Now, what we call decay is really the growth of these fungi. Animal and vegetable substances which these fungi seize upon are destroyed. All ordinary fermentations and putrefactions are due to mould fungi, yeast plants, or bacteria, and liquids undergoing these processes carry these fungi and their germs wherever they go. The refuse of the city pollutes the air. You have only to pass along any street to find more or less rubbish. That furnishes the nidus for the growth and development of these germs, and until we adopt better methods of getting rid of that refuse, we never shall have the air of this city in the condition that it should be.

One of the most constant sources of the pollution of the air in inhabited localities is the decomposition that takes place in the ground. Refuse of every kind gets into it. Our sewers are leaky, and putrefaction is constantly going on. The soil down to the limit of the ground water contains a large amount of air. This air, when the atmospheric pressure in the house is diminished, is drawn in with such organic impurities as it contains. A cement floor in the cellar is not a protection against this entrance of the ground air, for the cement is porous to the passage of air, but a remedy may be found by laying on the cement a covering of coal tar pitch, in which bricks are set on edge, the spaces between the bricks are filled with the melted pitch, and the bricks then covered with coal tar pitch. When the house is building, the foundation walls should also be similarly coated, outside as well as inside. Such a cellar floor was considered to be absolutely impervious to ground air and moisture. The lecturer had recently laid this floor in his own house with the greatest success. The atmosphere of the entire house is improved, and the expense is very moderate. Another source of the contamination of the air of houses is the heating apparatus. Stoves and furnaces, however well constructed at first, will, from the contraction and expansion of the metal, soon allow the escape of coal gas, and this danger is greatly increased by the use of dampers in the stove-pipe. When, to regulate the fire, the damper in the pipe is closed, the gases, having their passage to the chimney cut off, will escape through any cracks or openings in the stove into the room. Prof. Chandler, having kept a record of accidents from this cause, had accumulated a formidable list of suffocations due to the use of the damper. The danger was now somewhat lessened by providing dampers with perforations in the center, which allowed the gases to escape when the damper was closed. As regards the maintenance of pure air in houses, the preference was given to the open fire-place. The hot-air furnace deriving a supply of pure air from out of doors was, when properly constructed, a very satisfactory method of heating, but in city houses the mistake was often made of carrying the cold air duct of the furnace to the front of the house, where it was exposed to the dust of the streets. It should be taken from the rear end of the house, and carried some distance above the surface of the yard. It was an excellent expedient to insert in the cold air duct a wire screen to hold a layer of cotton to retain the floating impurities which might enter the air-box. This could be removed from time to time, and the cotton replaced. Steam heating has been objected to by many for reasons in no wise due to the apparatus, but to neglect in the use of it. The complaint of closeness where steam is used is due to the fact that a room containing a steam radiator can be heated with every door and window closed, and no fresh air admitted, while with stoves and open fire-places a certain quantity of fresh air must be admitted to maintain the fire. Where radiators are used, the ventilation of the rooms should, therefore, be looked after. Again, the complaint that steam apparatus has an unpleasant odor is due to the fact that the radiators are allowed to become covered with dust, which is cooked, and gives rise to the smells complained of. The radiator should be from time to time cleaned. When these precautions are taken, no means of heating is more satisfactory than steam.

Sewer gas is another source of contamination; this is a very indefinite term, to which formerly many false and exaggerated properties of causing specific diseases were attributed. It is now, however, recognized to mean simply the air of sewers, generally not differing very greatly from common air, containing a certain proportion of marsh gas, carbonic acid, and sulphureted hydrogen, etc. No one of these gases, however, is capable of producing the diseases attributed to sewer gas. Careful research has shown that it is the sewage itself, containing germs of specific disease, which is added to the air in the sewer by the breaking of bubbles of gas on its surface, which is the cause of the diseases associated with sewers.

An intimate connection is believed to exist between the germs of sewer air and diphtheria, and probably also between sewer air and scarlet fever. This sewer gas is to be excluded from our houses by proper systems of plumbing, and to such an extent have these now been perfected, that there is no objection to having plumbing fixtures in all parts of the house. This opinion has lately been objected to in the Popular Science Monthly, as it was at a meeting of the Academy of Medicine last spring, but on wholly insufficient grounds.

The objectors all insist that a trap will allow sewer gas to pass through it, and the experiments made at the Academy of Medicine showed that sulphureted hydrogen gas, etc., would so pass. The advocates of the trap have never denied that the water seal would absorb gases on one side and give them off on the other, but they do deny that, in the conditions existing in good plumbing, such gases will be given off in quantities to do any damage, and they confidently assert that the germ which is the dangerous element will not pass the seal at all. Pumpelly investigated the matter for the National Board of Health, and in no instance was he able to make the germ pass the seal of the trap. It is now proposed to set up against the weight of this scientific testimony the results of an investigator in Chicago, whose work was at once appropriated as an advertisement by stock jobbing disinfectant companies in a manner which raises a suspicion that the investigation was made in their interest. He described tersely the essentials of good plumbing, the necessity of a trap on the house drain, the ventilation of the soil-pipe, and the ventilation of the trap against siphonage. Of the first, he said that it offered protection to each householder against the entrance into his house of the germs of a contagious disease which passed into the common sewer from the house of a neighbor. Were the trap dispensed with, the contagion in the sewer would have free entrance into the houses connecting with it.

Prof. Chandler, in conclusion, alluded to the cordial relations now existing between the Board of Health and the majority of the master plumbers of the city. He said that for himself his opinion of the craft had greatly risen during his intimate connection with plumbers the last two years. He thought the majority of the jobs now done in the city are well executed. He believed that the Board of Health had not been obliged to proceed against more than eight master plumbers since the new law went into force. He called upon the Association to adopt a "code of ethics," which should define what an honest plumber can do and cannot do, and he illustrated his meaning by citing an extraordinary case of fraudulent workmanship which had been recently reported to him. His remarks on this point were greeted with frequent outbursts of applause.

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THE PLANTAIN AS A STYPTIC.

The following abstract of a paper read by Dr. Quinlan at the recent British Pharmaceutical Congress, may prove of interest to medical readers in this country, where the plant mentioned is a common weed:

"About a year ago Dr. Quinlan had seen the chewed leaves of the Plantago lanceolata successfully used to stop a dangerous hemorrhage from leech bites in a situation where pressure could not be employed. He had searched out the literature of the subject, and found that, although this herb is highly spoken of by Culpepper and other old writers as a styptic, and alluded to as such in the plays of Shakespeare, its employment seems to have died out. Professor Quinlan described the suitable varieties of plantain, and exhibited preparations which had been made for him by Dr. J. Evans, of Dublin, State apothecary. They dried leaves and powdered leaves, conserved with glycerine, for external use; the juice preserved by alcohol, as also by glycerine, for internal use; and a green extract. He gave an account of the chemistry of the juice, from which it appeared that it was not a member of the tannin series; and also described its physiological effect in causing a tendency to stasia in the capillaries of the tail of a goldfish, examined with a microscopic power of 400 X. He regarded its styptic power as partly mechanical and partly physiological. The juice, in large doses, he had found useful in internal hemorrhages. The knowledge of the properties of this plant he thought would be useful in cases of emergency, because it could be obtained in any field and by the most uninstructed persons."

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BACTERIA.

Bacteria, whether significant of disease or decline of health, are found more or less numerous in everything we eat and drink. The germs or spores of many kinds, known as termo, lineola, tenue, spirillum, vibriones, etc, exist in almost infinite numbers; some of the smallest are too small to be seen by the highest powers, which, being lodged in all vegetable and animal substances, spring into life and develop very rapidly under favorable circumstances. They develop most rapidly when decomposition commences, and seem to indicate the degree or activity of that decomposition, also hastening the same. They are found most numerous in the feces, and usually fully developed in the fresh evacuations of persons of all ages. They may be seen plainly under a thin glass with high powers with strong or clear light, when the material is much diluted with water.

These bacteria appear almost as numerously, yet more slowly, in urine, either upon exposure to air or when freshly evacuated, when the general health of the individual is declining, or any tendency to decomposition. A diagnosis can be aided very greatly by a study of these bacteria, as they indicate or determine the vitality, vigor, and purity of the system, whether more or less subject to disease, even before any signs of disease appear. They seem to preindicate the hold of the life force on the material, and always appear when that force is broken. Their relative quantity found in feces is as a barometric indication of the general health or some particular disturbance, and it is surprising how very fast they multiply while simply passing the intestines under circumstances favorable for their growth. These forms, so small, are important, because so very numerous, and their study has been, perhaps, avoided by many; yet they certainly mean something and effect something, even the non-malignant varieties as mentioned above, and it is certainly worth while to continue to study their meaning, even beyond what has already been written by others on the subject.—J.M. Adams, in The Microscope.

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THE SOY BEAN

(Soja hispida.)

A good deal of attention has lately been directed to this plant in consequence of the enormous extent to which it is cultivated in China for the sake of the small seeds which it produces, and which are known as soy beans. These vary considerably in size, shape, and color, according to the variety of the plant which produces them. They are for the most part about the size and shape of an ordinary field pea, and, like the pea, are of a yellow color; some, however, are of a greenish tint. These seeds contain a large quantity of oil, which is expressed from them in China and used for a variety of purposes. The residue is moulded with a considerable amount of pressure into large circular cakes, two feet or more across, and six inches or eight inches thick. This cake is used either for feeding cattle or for manuring the land; indeed, a very large trade is done in China with bean cake (as it is always called) for these purposes. The well-known sauce called soy is also prepared from seeds of this bean. The plant generally known as Soja hispida is by modern botanists referred to Glycine soja. It is an erect, hairy, herbaceous plant. The leaves are three-parted and the papilionaceous flowers are born in axillary racemes. It is too tender for outdoor cultivation in this country, but, has been recommended for extended growth in our colonies as a commercial plant. The plants are readily used from seed.—J.R.F., in The Garden.



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ERICA CAVENDISHIANA.

The plant of which the illustration is given is one of those fine specimens which has made the collection of J. Lawless, Esq., The Cottage, Exeter, famous all over the south and west of England. It is only one specimen among a considerable collection of hard-wooded plants which are cultivated and trained in first rate style by Mr. George Cole, the gardener, one of the most successful plant growers of the day. The plant was in the winning collection of Mr. Cole exhibited at the late spring show held at Plymouth.—The Gardeners' Chronicle.



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PHILESIA BUXIFOLIA.

We figure this plant, not as a novelty, but for the purpose of showing what a fine thing it is when grown under propitious circumstances. Generally, we see it more or less starved in the greenhouse, and even when planted out in the winter garden its flowers lack the size and richness of color they attain out-of-doors. It comes from the extreme south of South America, which accounts for its hardihood, and is a near ally of the Lapageria: the latter is remarkable for withstanding even the noxious fumes of the copper smelting works in Chili, and as the Philesia has similar tough leaves, it is probable that it would support the vitiated atmosphere of a town better than most evergreens. In any case, there is no reasonable doubt but that, if cultivators would take the necessary pains, they might select perfectly hardy varieties both of the Lapageria and of the Philesia. As it is, we can only call the Philesea half-hardy north of the Thames, while the Lapageria is not even that. The curious Philageria, raised in Messrs. Veitch's nursery and described and figured in our columns in 1872, p. 358, is a hybrid raised between the two genera. For the specimen of Philesia figured we are indebted to Mr. Dartnall.—The Gardeners' Chronicle.



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MAHOGANY.

The mahogany tree, says the Lumber World, is a native of the West Indies, the Bahamas, and that portion of Central America that lies adjacent to the Bay of Honduras, and has also been found in Florida. It is stated to be of moderately rapid growth, reaching its full maturity in about two hundred years. Full grown, it is one of the monarchs of tropical America. Its trunk, which often exceeds forty feet in length and six in diameter, and massive arms, rising to a lofty height, and spreading with graceful sweep over immense spaces, covered with beautiful foliage, bright, glossy, light, and airy, clinging so long to the spray as to make it almost an evergreen, present a rare combination of loveliness and grandeur. The leaves are small, delicate, and polished like those of the laurel. The flowers are small and white, or greenish yellow. The fruit is a hard, woody capsule, oval, not unlike the head of a turkey in size and shape, and contains five cells, in each of which are inclosed about fifteen seeds.

The mahogany tree was not discovered till the end of the sixteenth century, and was not brought into European use till nearly a century later. The first mention of it is that it was used in the repair of some of Sir Walter Raleigh's ships, at Trinidad, in 1597. Its finely variegated tints were admired, but in that age the dream of El Dorado caused matters of more value to be neglected. The first that was brought to England was about 1724, a few planks having been sent to Dr. Gibbons, of London, by a brother who was a West Indian captain. The doctor was erecting a house, and gave the planks to the workmen, who rejected them as being too hard. The doctor then had a candle-box made of the wood, his cabinet-maker also complaining of the hardness of the timber. But, when finished, the box became an object of general curiosity and admiration. He had one bureau, and her Grace of Buckingham had another, made of this beautiful wood, and the despised mahogany now became a prominent article of luxury, and at the same time raised the fortunes of the cabinet-maker by whom it had been so little regarded. Since that lime it has taken a leading rank among the ornamental woods, having come to be considered indispensable where luxury is intended to be indicated.

A few facts will furnish a tolerably distinct idea of the size of this splendid tree. The mahogany lumbermen, having selected a tree, surround it with a platform about twelve feet above the ground, and cut it above the platform. Some twelve or fifteen feet of the largest part of the trunk are thus lost. Yet a single log not unfrequently weighs from six or seven to fifteen tons, and sometimes measures as much as seventeen feet in length and four and a half to five and a half feet in diameter, one tree furnishing two, three, or four such logs. Some trees have yielded 12,000 superficial feet, and at average price pieces have sold for $15,000. Messrs. Broadwood London, pianoforte manufacturers, paid 3,000 for three logs, all cut from one tree, and each about fifteen feet long and more than three feet square. The tree is cut at two seasons of the year—in the autumn and about Christmas time. The trunk, of course, furnishes timber of the largest dimensions, but that from the branches is preferred for ornamental purposes, owing to its closer grain and more variegated color.

In low and damp soil its growth is rapid; but the most valuable trees grow slowly among rocks on sterile soil, and seem to gather compactness and beauty from the very struggle which they make for an existence. In the Bahamas, in the most desolate regions, once flourished that curiously veined and much esteemed variety once known in Europe as "Madeira wood," but which has long since been exterminated. Jamaica, also, which used to be a fruitful source of mahogany, and whence in 1753 not less than 521,000 feet were shipped, is now almost depleted. That which is now furnished from there is very inferior, pale, and porous, and is less esteemed than that of Cuba, San Domingo, or Honduras.

In a dry state mahogany Is very durable, and not liable to the attack of worms, but, when exposed to the weather it does not last long. It would therefore make excellent material for floors, roofs, etc., but its costliness limits its utility in this direction, and it is chiefly employed for furniture, doors, and a few other articles of joinery, for which it is among the best materials known. It has been used for sashes and window frames, but is not desirable for this purpose on account of the ease with which it is affected by the weather. It has also been used in England to some extent for the framing of machinery in cotton-mills. Its color is a reddish brown of different shades and luster, sometimes becoming a yellowish brown, and often much veined and mottled with darker shades of the same color. Its texture is uniform, and the rings indicating its annual growth are not very distinct. The larger medullary rays are absent, but the smaller ones are often very distinct, with pores between them. In the Jamaica woods these pores are often filled with a white substance, but in that brought from Central America they are generally empty. It has neither taste nor odor, shrinks very slightly, and warps, it is said, less than any other wood.

The variety called Spanish mahogany comes from the West Indies, and is in smaller logs than the Honduras mahogany, being generally about two feet square and ten feet long. It is close grained and hard, generally darker than the Honduras, free from black specks, and sometimes strongly marked; the pores appear as though chalk had been rubbed into them.

The Honduras mahogany comes in logs from two to four feet square and twelve to fourteen long; planks have been obtained seven feet wide. Its grain is very open and often irregular, with black or gray specks. The veins and figures are often very distinct and handsome, and that of a fine golden color and free from gray specks is considered the best. It holds the glue better than any other wood. The weight of a cubic foot of mahogany varies from thirty-five to fifty-three pounds. Its strength is between sixty-seven and ninety-six, stiffness seventy-three to ninety-three, and toughness sixty-one to ninety-nine—oak being considered as one hundred in each case.

There are three other species of the genus Swietania besides the mahogany tree, two of them natives of the East Indies. One is a very large tree, growing in the mountainous parts of central Hindostan, and rises to a great height, throwing out many branches toward the top. The head is spreading and the leaves bear some resemblance to those of the American species. The wood is a dull red, not so beautiful as that known to commerce, but harder, heavier, and more durable. The natives of India consider it the most durable timber which their forests afford, and consequently use it, when it can be procured, wherever strength and durability are particularly desired. The other East Indian species is found in the mountains of Sircars, which run parallel to the Bay of Bengal. The tree is not so large as any of the other species described, and the wood is of much different appearance, being of a deep yellow, considerably resembling box. The grain is close, and the wood both heavy and durable. The third species, known as African mahogany, is brought from Sierra Leone. It is hard and durable, and used for purposes requiring these properties in an eminent degree. If, however, the heart of the tree be exposed or crossed in cutting or trimming the timber, it is very liable to premature and rapid decay.

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ANIMALS AND THE ARTS.

In many of the museums efforts are made to perfect economic collections of animals, so as to show how they can be applied to advantage in the arts and sciences. The collection and preparation of the corals, for example, form an important industry. The fossil corals are richly polished and set in studs and sleeve-buttons, forming rich and ornamental objects. The fossil coral that resembles a delicate chain has been often copied by designers, while the red and black corals have long been used. The best fisheries are along the coasts of Tunis, Algeria, and Morocco, from 2 to 10 miles from shore, in from 30 to 150 fathoms. Good coral is also common at Naples, near Leghorn and Genoa, and on various parts of the sea, as Sardinia, Corsica, Catalonia, Provence, etc. It ranges in color from pure white through all the shades of pink, red, and crimson. The rose pink is most valued. For a long time Marseilles was the market, but now Italy is the great center of the trade, the greater number of boats hailing from Torre del Greco, while outside persons are forced to pay a heavy tax. The vessels are schooners, lateen-rigged, from three to fourteen tons. Large nets are used, which, during the months between March and October, are dragged, dredge-like, over the rocks. A large crew will haul in a season from 600 to 900 pounds. To prevent the destruction of the industry, the reef is divided into ten parts, only one being worked a year, and by the time the tenth is reached the first is overgrown again with a new growth. In 1873 the Algerian fisheries alone, employing 3,150 men, realized half a million of dollars. The choice grades are always valuable, the finest tints bringing over $5 per ounce, while the small pieces, used for necklaces, and called collette, are worth only $1.50 per ounce. The large oval pieces are sent to China, where they are used as buttons of office by the mandarins.

THE CONCH-SHELL.

Somewhat similar in appearance to coral is the conch jewelry, sets of which have been sold for $300. The tint is exquisite, but liable to fade when exposed to the sun. It is made from the great conch, common in Southern Florida and the West Indies. The shells are imported into Europe by thousands, and cut up into studs, sleeve-buttons, and various articles of ornament. These conches are supposed to be the producers of pink pearls, but I have opened hundreds of them and failed to find a single pearl. The conch shell is used by the cameo cutter. Rome and Paris are the principal seats of the trade, and immense numbers of shell cameos are imported by England and America, and mounted in rings, brooches, etc. The one showing a pale salmon-color upon an orange ground is much used. In 1847, 300 persons worked upon these shells in Paris alone, the number of shells used being immense. In Paris 300,000 helmet-shells were used in one year, valued at $40,000 of the bull's mouth, 80,000, averaging a little over a shilling apiece, equal to $34,000. Eight thousand black helmets were used, valued at $9,000. The value of the large cameos produced in Paris in the year 1847 was about $160,000, and the small ones $40,000. In the Wolfe collection of shells at the Museum of Natural History, Central Park, is a fine specimen of the queen conch from the Florida reef, with a fine head cut into the outer surface, showing how it is done. The tools of the worker in cameos are of the most delicate description. Fine files, knitting-needle like implements, triangular-shaped steel cutters, are arranged in a seemingly endless confusion before the worker. The shell or piece of shell to be cut is either lashed or glued to a heavy block or held in the hand, and the face, animal, or other object outlined first with a delicate lead; having thus laid the foundation, the lines are gone over with a delicate needle first, then various kinds, the work gradually growing before the eye, reminding one of the work of the engraver on wood.

LIVING BEETLES, ETC.

Insects have always been used more or less in decoration, especially in Brazil, where the richly-colored beetles of the country are affected as articles of personal adornment. Recently in a Union Square jewelry store a monster beetle was on exhibition, having been sent there for repairs. It was alive, and about its body was a delicate gold band, locked with a minute padlock; a gold chain attached it to the shawl of the owner. Sometimes they are worn upon the headgear, their slow, cumbersome movements preventing them from attracting great attention. They are valued at from $50 to $100 apiece. Snakes, the rich green variety so common in New England, are worn by some ladies as bracelets, while the gorgeous reptiles are often imitated in gold and silver, with eyes of diamonds, rubies, or black pearls. Gold bears are the proper thing now for pins. In the East the chameleon is often worn as a head ornament, the animal rarely moving, and forming at least a picturesque decoration, with its odd shape and sculptured outlines. Various other reptiles, as small turtles, alligators, etc., are pressed into service. The curious soldier-crab has been used as a pin. Placed in a box with a rich pearly shell prepared for the purpose, it will change houses, and then, secured by a gold or silver chain, roams about the wearer, waving its red and blue claws in a warlike manner. Birds are, perhaps, more commonly used as natural ornaments than any other, and a cloak of the skins of humming birds is one of the most magnificent objects to be imagined. One, of a rare species, was once sold in Europe for $5,000. Single birds are often worth $700 or $800. A cloak of the skin of the great auk would bring $8,000 or $10,000. Some of the most beautiful pheasants are extremely valuable—worth their weight in gold. Tiger claws are used in the decoration of hats, and are extremely valuable and hard to obtain.

Within ten years the alligator has become an important factor to the artistic manufacturer. The hide, by a new process, is tanned to an agreeable softness and used in innumerable ways. The most costly bags and trunks are made from it; pocket-books, card-cases, dining-room chairs are covered with it, and it has been used as a dado on the library wall of a well-known naturalist. It makes an excellent binding for certain books. Among fishes the shark provides a skin used in a variety of ways. The shagreen of the shark's ray is of great value. Canes are made of the shark's backbone, the interstices being filled with silver or shell plates. Shark's teeth are used to decorate the weapons of various nations. The magnificent scales, nearly four inches across and tipped with seemingly solid silver, of the giant herring, are used, while scales of many of the tribe have long been used in the manufacture of artificial pearls.

PEARLS.

The latter are perhaps the most valuable of all the offerings of animate nature, and are the results of the efforts of the bivalve to protect itself from injury. A parasite bores into the shell of the pearl bearer, and when felt by the animal it immediately fortifies itself by covering up the spot with its pearly secretion; the parasite pushes on, the oyster piling up until an imperfect pearl attached to the shell is the result. The clear oval pearls are formed in a similar way, only in this case a bit of sand has become lodged in the folds of the creature, and in its efforts to protect itself from the sharp edges, the bit becomes covered, layer by layer, and assumes naturally an oval shape. This growth of the pearl, as it is incorrectly termed, can be seen by breaking open a $500 gem, when the nacre will be seen in layers, resembling the section of an onion. The Romans were particularly fond of pearls, and, according to Pliny, the wife of Caius Caligula possessed a collection valued at over $8,000,000 of our money. Julius Caesar presented a jewel to the mother of Brutus valued at $250,000, while the pearl drank by Cleopatra was estimated at $400,000. Tavernier, the famous traveler, sold a pearl to the Shah of Persia for $550,000. A twenty-thousand-dollar pearl was taken from American waters in the time of Philip II. It was pear-shaped, and as large as a pigeon's egg. Another, taken from the same locality, is now owned by a lady in Madrid who values it at $30,000.

Fresh water pearls are often of great value. The streams of St. Clair County. Ill., and Rutherford County, Tenn., produce large quantities, but the largest one was found near Salem, N. J. It was about an inch across, and brought $2,000 in Paris. The pearls from the Tay, Doon, and Isla rivers, in Scotland, are preferred by many to the Oriental, and in one summer $50,000 worth of pearls have been taken from these localities by men and children. Mother-of-pearl used in the arts is sold by the ton, from $50 to $700 being average prices. The last year's pearl fisheries in Ceylon alone realized $80,000, to obtain which more than 7,000,000 pearl oysters were brought up.

SEPIA AND SILK.

The sepia of the artist comes from a mollusk, and is the fossil or extant ink-bag of a cephalopod or squid, while the cuttle-fish bone is used for a variety of purposes. In the islands of the Pacific the young of the pearly nautilus are strung upon strings and sold for $25 and $20 as necklaces. The tritons are in fair demand, and many tons of cowries are sent to Europe yearly, while the shipment of a thick-lipped strombus in one year to Liverpool amounted to 300,000. The rich coloring of the haliotis is used for inlaying art furniture. From the pinna, silk of a peculiar quality is obtained. It is the byssus or cable of the animal. The threads are extremely fine, and equal in diameter throughout their entire length. It is first cleaned with soap and water, and dried by rubbing through the hands, and finally passed through combs of bone, iron, or wood, of different sizes, so that a pound of the material in the rough gives only about three ounces of pure thread. It is mixed with a third of real silk and spun into gloves, stockings, etc., having a beautiful yellow hue. The articles made from it are, however, not in general use. A pair of gloves from pinna silk would cost $1.50, and stockings about $3. Fine specimens of such work can be seen in the British Museum.

Though not of animal origin, amber is one of the choicest vegetable productions used in the arts. It is the fossil gum of pines. Great beds of it occur at various points in Europe. On the Prussian seaboard it is mined, and often washes ashore. In 1576 a piece of amber was found that weighed thirteen pounds, and for which $5,000 was refused. In the cabinet of the Berlin Museum there is a piece weighing eighteen pounds. Ambergris, from which perfumery is made, is a secretion taken from the intestines of the whale, and a piece purchased from the King of Tydore by the East India Company is reported to have cost $18,000. Whales' teeth, the tusks of elephants, and those of the walrus and narwhal, are all used. Elephants' feet are cut off at a convenient length, richly upholstered, and used as seats; the great toe-nails, when finely polished, giving the novel article of furniture an attractive and unique appearance.

It is probably not generally known that the web of certain spiders has been used. Over 150 years ago, Le Bon, of France, succeeded in weaving the web material into delicate gloves. Prof. B.G. Wilder investigated the question thoroughly, and was a firm believer that the web of the spider had a commercial value, but as yet this has not been realized. It would be difficult to find an animal that does not in some way contribute to the useful or decorative arts.—C.F.H., in N.Y. Post.

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