CHAPTER V.GUTTA-PERCHA FOR BELTS, HARNESSES, &C.

Belts of leather may be put together by this cement, which adds greatly to their wear and durability, not being in the least affected by dampness, neither by the oils which may come in contact with them from the machinery. In cutting up belt for harness leather, there is usually great waste and loss of stock, as portions of the sides are very thin, and unfit for use. But by this process every particle may be saved. Cut the stock the proper width, stretch it, then raise a strong thick fibre on all the thin parts and the laps. Apply the cement hot with a brush to all the thin portions and laps. Let it dry until the solvent has evaporated; then heat the parts sufficiently, and press together with a vice or clamps. On all the thin places apply a piece of the cemented leather until the belt is of an even thickness; press firmly together, then shave off the projections with a knife or cutting machine. Trim the edges: you will thus produce a firm, smooth belt,without a stitch, rivet, or lacing. All portions of a harness or saddle may be cemented in the same manner. This process is exceedingly simple, at the same time economical—asaving of time and money, and adds greatly to their durability.

It may be applied to vats, drains, cisterns, sinks, etc., to great advantage. All square joints should be first prepared by raising a fibre, as in veneering work. Apply the cement hot, as glue is spread. In a few hours the solvent will evaporate; then heat the parts sufficiently to melt the cement; press together firmly. The gutta-percha will be found to be an excellent cement for all leaky places in stone, brick or wood work. Mix it with sand, or any fibrous substance, apply hot, or melt it in with a hot iron. Thepuregutta-percha will cement broken stone, marble or brick, so firmly that it will remain for years. It is undoubtedlythe best cement ever yet discovered. Ornamental work, centre-pieces, etc., may be thus cemented to their position.

It is a well known fact, that sub-marine wires, enclosed in the gutta-percha tube, areindestructible, as all sea insects, worms, &c., never molest it. In caulking all ships, boats, &c., oakum, oranyfibrous substance, may be saturated withpuregutta-percha, and then pressed hot into the joints with a hot iron. This process renders the jointsproof against all agencies. The joint thus cemented is mademore firm and solid than the plank itself.

TESTIMONIALSCONCERNING THE PRACTICAL VALUE OF GUTTA-PERCHA, AND ITS APPLICATION TO BOOTS AND SHOES, IN LONDON.

Gutta-Percha Company of London, Oct. 1st, 1849.

The application of gutta-percha soles for boots and shoes have been extensively and satisfactorily tested, its merits having been acknowledged by all who have worn them. Indeed, experience has proved thatgutta-perchasoles weartwice as long as leather, with great additional personal comfort, and remainperfectly impervious to wetuntil worn through.

Southampton Row, Sept. 1st, 1847.

Gentlemen: I write to thank you because I can speak confidently of the advantages of gutta-percha over leather soles. I made the first pair last October, and wore themeight monthsbefore I wore the soles through. I had them heeled six times, and one pair of extrafrontsI put to thesamesoles. I only kept one pair in use to see how long they would last. I will never wear another leather sole so long as I can obtain gutta-percha soles, and I walk from twelve to twenty miles a day.

C. Wright,Boot and Shoe Maker.

C. Wright,

Boot and Shoe Maker.

To the Gutta-Percha Co.

Gutta-Percha Company’s Works.

Patent Gutta-Percha Soles.—The applicability of gutta-percha soles for boots and shoes having been extensively and satisfactorily tested, we can unhesitatinglyrecommend the material prepared for the purpose, its merits having been acknowledged by all who have tried it. Indeed, experience has proved that gutta-percha soles weartwice as long as leather, with greatadditional personal comfort, and they remainperfectly impervious to wet, until quite worn through.

London, Nov. 4th, 1847.

Gentlemen:—I have given the gutta-percha boot soles what may be considered a fair trial, namely:three month’s constant wearon a rough, gravelly road, and can bear testimony to its usefulness.With proper care in putting them on, and a little attention afterwards, I am persuaded that it will last longer than leather, and being impervious to wet, will be found invaluable to persons subject to damp or cold feet.

W. Diar,Principal Officer of H. M. Customs, Whitstable.

W. Diar,

Principal Officer of H. M. Customs, Whitstable.

Manchester, England, March 8, 1848.

To Mr. Henry Statham:

Dear Sir:—It is with pleasure that I bear testimony to the good qualities of gutta-percha soles. You are aware that my occupation requires me to be on foot a great deal, upon all kinds of roads, and in all weathers, and since I began to wear gutta-percha soles, I havenot hadto complain ofwet or cold feet. The pair I have on now have been in almost daily use for more than four months, and my fear is, that the upper leather will be worn out first. I am quite sure thatI save from thirty to fifty per cent., in the cost of shoes, in consequence of my family wearing gutta-perchasoles, and, so long as I can get them, I intend to wear them in preference to anything else I have seen.

Yours respectfully,Thomas Whitehead,Gas Office, Town Hall, King Street.

Yours respectfully,

Thomas Whitehead,

Gas Office, Town Hall, King Street.

London, April 1, 1848.

Gutta-percha Boot and Shoe Soles for Summer Wear.—The fact of the total imperviousness of these soles to water, enables the most delicate, by the use of them to escape the suffering which the proverbial uncertainty of our climate, even in summer, so often inflicts upon the incautious. All injurious effects may be entirely prevented by a sole so thin and light, as to afford to the wearer a degree of ease and comfort, unattainable in conjunction with security against damp. At the same time theremarkable nonconducting propertiesof gutta-percha, afford a most valuable protection to those who are subject to suffering or inconvenience by walking upon heated pavements. No instance of failure has ever come to the knowledge of the company, which may not be ascribed to the neglect of the wearer.

The following article from theLondon Weekly Despatchwill be read with interest. The writer has, evidently, not only a knowledge of the subject upon which he writes, but an appreciation of the value of gutta-percha, and its invaluable importance in the mechanical arts.

“We have lately visited the extensive works belonging to the Gutta-Percha Company, in Wharf-road City-road, and confess that we were delighted andastonished. The premises in which the business of the company is carried on cover a large area of ground. Several floors of the building are devoted to the operations of the workmen, amounting to nearly one hundred and seventy individuals, including a sprinkling of stout, hearty-looking boys. The basement is occupied by two steam-engines, without whose presence the works would by no means be complete. These groan from “early morn to dewy eve,” in turning lathes in the engineering department, in kneading the gutta-percha, cutting out soles and heels for boots and shoes, rolling out driving bands of every dimension, and heating the steam-chests by which the gutta-percha is rendered pliable and fit for the hands of the workmen. On the principal floor there are several hydraulic presses, used in the process of manufacture; and we had the good fortune to witness the production of a complete dessert service of the most chaste and elegant pattern, and in imitation of gnarled oak. The subjects of adornment were brought out in high relief, and after undergoing the process of varnishing, were surprisingly beautiful, light, and incapable of being fractured or broken by a fall or blow.”

Some of these sets were of the vine-leaf pattern, in close imitation to nature. These things were pressed out with some rapidity, but not without great manual labor, notwithstanding the aid of the powerful presses alluded to. Inkstands of the most beautiful character were also fashioned in a short time; indeed, all sorts of ornaments, elaborated with the most ingenious devices, were made during our stay. We observed avast deal of ornamental work, intended to supersede the labor of the carver. There were frames of large dimensions ready for the reception of pictures. We were particularly struck with the appearance of one intended for a large pier-glass. The foliage was of the most sumptuous workmanship, and possessed a sharpness and finish which the hand of man could scarcely accomplish. A design for a bible cover was exhibited. The subject harmonized with the nature of the book it was intended to enclose, and was in bold relief. It is believed that gutta-percha will, in a short time, be in general use among book-binders, not only in the shape of massive covers, but to supersede the present cotton binding which has so pretty an appearance, but is not of that lasting character as to induce persons to adopt it in cases where strength and durability are required. In other portions of the factory, workmen were employed in making instruments used by surgeons, to be employed in cases of a delicate nature; others were finishing off the numerous objects just turned out of the moulds. Amongst the other articles of curiosity, we observed several yards of gutta-percha rendered exceedingly thin by machinery, andintendedforladies’ dresses. It was of a light pink color, by no means displeasing to the eye, and possessed of great strength. By the aid of delicate machinery, the gutta-percha was run out into thread, to be used in the manufacture of ladies’ work bags, fishing nets, and for a hundred other purposes.

Large tubing, and some with an inconceivably small bore, was run out to lengths of various dimensions. Wagon and cart harness, of enormous strength, combinedwith lightness, we observed hanging up in the establishment, besides gentlemen’s riding-whips, and things of every kind. Greatly as we were delighted with all these things, we had yet another treat to come, which infinitely surpassed anything we had seen. We were shown several specimens of enormous panelling, on which the carving of the original design was brought up with remarkable fidelity. Considering that gutta-percha is an indestructible material, we have little hesitation in stating, that the mansions of the nobility will soon be decorated with ornamental work produced by this new system of multiplying objects, produced by the ancients to their glory and eternal honor.

CHAPTER VI.INDIA-RUBBER, ITS DISCOVERY, USES, &C.

This important gum is known by a variety of names. Caoutchouc, gum-elastic, and India-rubber. It is a product of the syringe tree of South America. This substance was first brought to Europe in 1735, by some French astronomers, who were sent to Brazil to make astronomical observations. It is found abundantly in Peru, Brazil, and Quito, and has recently been discovered in Asia. Considerable quantities of it are now obtained in Java, Penang, Singapore and Assam. In some places hundreds of miles are covered with trees. They are very lofty, rising to the height of fifty or sixty feet, without branches, but covered with a rich tufted foliage. The bark is exceedingly smooth, its leaves deep green, thick and glossy, and six or seven inches in length. The fruit consists of white almonds and is regarded by the natives as very delicious. The process of obtaining the liquid is very simple. A longitudinal gash is cut in the bark of the tree with a hatchet, a wedge is then inserted to keep the aperture open; the gumthen oozes out in the form of a milky juice. A small clay cup is attached to the tree into which the sap flows. In the space of four or five hours the milk ceases to run, and the quantity received is about five table spoonsful. The cups are now emptied and the process of smoking is commenced; this with the forming process must be done as soon as the milk coagulates. A fire is built upon the ground made of the nuts of the wassou palm tree; over this fire an inverted earthen pot, with a hole in the bottom is placed, from whence issues a jet of pungent smoke. The smoke changes the color of the gum very slightly at first, but by exposure to the atmosphere it becomes first brown, then quite black, presenting the appearance which we see it has in articles of commerce. The sap of the tree is laid on a mould in successive layers, which are allowed to dry, and are formed into bottles and cakes, in which form it is exported. The natives of South America are very ingenious in the uses to which they apply it. Boots, shoes,syringes, and tubes, are among the many articles of domestic use into which it is converted. The tubes they use as torches, which burn very clearly, and emit but little odor. According to the celebrated chemist, Faraday, its composition is carbon, 87.2, hydrogen, 12.8—a hydro-carbon. It melts when exposed to a heat of 248°, and is resolved into vapor at 600°, and can be condensed into a liquid called caoutchoucin. In 1770, a cubic inch of India-rubber was sold in London for seventy-five cents, to erase pencil marks. It was not used to make water-proof fabrics until about the year 1800. These were first invented by Charles Mackintosh, of Glasgow, who applied a naptha solution to the surface of two pieces of cloth, then laid them together, passed them between rollers and thus cemented them together.

NATIVES GATHERING GUTTA-PERCHA.

A “Mackintosh” was the name applied for many years to a water-proof coat. Dr. Ure, although well aware of Mr. Mackintosh’s invention, coldly passes it over in his dictionary. It is supposed that personal feeling was the cause of this, as Dr. Thomson and Ure were once rival chemists in Glasgow, and Mackintosh was the friend and pupil of the former. The fabrics of Mackintosh had a most disagreeable smell, still he was the first person who established India-rubber manufactures in Britain, and perhaps the world. He afterwards removed his factory to Manchester, England. Various kinds of goods made of India-rubber soon afterwards began to be manufactured in England, but they were all decidedly objectionable to use, until the grand discovery of sulphurization was made; for this the world is indebted to anAmerican inventor, Nathaniel Hayward of Woburn, Mass.

This substance, or rather, compounds of it, is now manufactured into so many articles of beauty and usefulness, that it forms an object of no small wonder to witness the rapidity with which such manufactures have sprung into existence.

The following description of the India-Rubber tree and its fruit is given by Chevalier D. Claussen, inventor of the flax cotton. He says that in the course of his travels in South America, he had occasion to notice the different trees which produce the India-rubber, and of which theHancornia speciosais one. It grows on the high plateaux of South America, between the tenth and twentieth degrees of latitude south, at a height of from three to five thousand feet above the level of the sea. It is of the family of theSapotacæ, the same to which belongs the tree which produces gutta-percha. It bears a fruit, in form, not unlike a bergamot pear, and full of a milky juice, which is liquid India-rubber. To be eatable, the fruit must be kept two or three weeks after being gathered, in which time all the India-rubber disappears, or is converted into sugar, and is then in taste one of the most delicious fruits known, and regarded by the Brazilians (who call it Mangava) as superior to all other fruits of their country. The change of India-rubber into sugar, led him to suppose that gutta-percha, India-rubber, and similar compounds contained starch. He therefore tried to mix it with resinous or oily substances, in combination with tannin, and succeededin making compounds which can be mixed in all proportions with gutta-percha or India-rubber without altering their characters. By the foregoing it will be understood that a great number of compounds of the gutta-percha and India-rubber class may be formed by mixing starch, gluten, or flour with tannin and resinous or oily substances. By mixing some of these compounds with gutta-percha or India-rubber, he can so increase its hardness that it will be like horn, and may be used as shields to protect the soldiers from the effect of the Minie balls, and some of these compounds in combination with iron, may be useful in floating batteries and many other purposes, such as covering the electric telegraph wires, imitation of wood, ship-building, &c.

A description of the various uses to which India-rubber is applied, will be found exceedingly interesting and instructive. The English have thus far succeeded more perfectly, or rather more generally in their application of it, than we, although since 1856, rapid strides have been made in perfecting the manufacture of the various fabrics in which it is used in our country, especially New England. It must not be forgotten that to an American is due the discovery of the process of sulphurization, which discovery immediately gave a new value, and a new impulse to the application of this wonderful product of the forests of South America.

The following account of the various uses to which India-rubber is applied, is taken principally from English sources, and refers to the manufactures of that country.

INDIA-RUBBER CLEANING PROCESSES.

The India-rubber, or caoutchouc, now imported to the enormous extent of six or seven hundred thousand pounds annually, reaches this country in masses of varied shape, but mostly of a dark color. In its imported state it is used for very few purposes; considerable modifications being necessary for its adaptation to practical service. It requires to be transformed into cakes, or sheets, or tissues, or tubes, or solutions, preparatory to its ultimate use; and this transformation requires operations of a somewhat peculiar kind, owing to the necessity of rendering the whole mass homogeneous in substance.

The bottles, and masses, and fragments, as imported, have much inequality in texture, and are, moreover, contaminated with much dirt and refuse. To separate these, the India-rubber is first cut into very small fragments, and then steeped in warm water, by which the dirt is precipitated. The fragments are dried, and are then thrown into a kind of kneading machine, where immense pressure is employed to bring them to one homogeneous mass. The India-rubber, though put in cold, becomes so hot by the agitation that it could not be safely touched by the hand; it is necessary to supply the machine with cold water, which is made nearly to boil by the caloric driven out of the elastic mass. So thoroughly is the mass pressed, rolled, pricked, cut, and kneaded, by the severe turmoil which it undergoes, that all dirt, air, water and steam are expelled, and it presents the appearance of a dark colored, uniform, smooth mass. It is put into cast iron moulds of great strength, and brought, byhydraulic or screw pressure, to the form of blocks, slabs, or cylinders, according to the purpose to which it is to be applied.

The manufacture of the Mackintosh cloth is a singular one. The material is merely two layers of cotton cemented with liquid India-rubber; but the junction is so well effected, that the three become to all intents and purposes one. The stout and well-woven cloth is coiled upon a horizontal beam, like the yarn beam of a loom; and from this it is stretched out in a tight state and a nearly horizontal position. A layer of liquid or rather paste-like solution is applied with a spatula, to a considerable thickness, and the cloth is drawn under a knife edge, which scrapes the solution and diffuses it equally over every part of the cloth, which may be thirty or forty yards long. The cloth is then extended out on a horizontal framework to dry; and, when dried, a second coating is applied in a similar way; and a third and fourth may be similarly applied if necessary. Two pieces, thus coated, are next placed face to face with great care, to prevent creasing or distortion; and, being passed between two smooth wooden rollers, they are so thoroughly pressed as to be made to unite durably and permanently. Cloth, thus cemented and doubled and dried, may be cut and made into garments which will bear many a rough trial, and many a deluging before rain or water can penetrate.

INDIA-RUBBER CUTTING PROCESSES.

It is as asheetand as athreadthat India-rubber meets its most extensive application; and both of these are made by cutting from the blocks and slabs. A block is cut into sheets by an ingenious machine, in which a sharp knife-edge has a rapid vibratory motion in a horizontal plane, so adjusted as to cut a thin film from a block of India-rubber supplied to it by a steady motion. The knife requires to be kept cool by a flow of water, or it would adhere to the India-rubber. In this way thin sheets may be cut, or thicker sheets from which stationers’ India-rubber may be obtained, or sheets of any thickness, great or small, according to the purposes required.

The separation of the material into shreds or narrow strips is a very pretty operation, exhibiting much nicety of manipulation. A continuous strip may be cut from a bottle or any other curved mass of the India-rubber. The bottom of the bottle is cut off, and is pressed into a round and tolerably flat form. The cake thus fashioned is fixed to the end of the horizontal shaft, or lathe-axis, and is made to revolve with great rapidity; and while so rotating, a circular knife, rotating at high speed, cuts through the substance, and advances steadily towards the centre of the disc; thereby separating the disc or cake into one continuous spiral thread. This thread can be easily drawn out straightly, and can even be separated into two or more finer threads, by drawing it through a hole where one or more sharp-cutting edges encounter it. If a bottle or any other hollow piece of India-rubber can be drawn over a cylinder ofuniform diameter, it may be cut into a continuous thread, by a modification of the same machine; the cylinder being made to revolve, a steel cutter is placed against it, and as the cylinder has a slow longitudinal motion given it, the gum is cut spirally from end to end—just on the same principle as a worm or thread is cut on a bit of iron by the screw-cutting machine. Machines of this kind were invented in France more than twenty years ago; but the machines used in our own country are of English invention and of later date.

When once it was discovered that India-rubber may be dissolved in petroleum, in naptha, or in oil of turpentine, it was speedily seen that a new and extensive sphere of utility was given to it. The coarsest pieces, as imported, the waste from the kneading operations, and the parings and cuttings from other manufacturing operations, are placed in a close iron vessel, to which the liquid solvent is added. A brisk agitation is kept up, and the heat thereby generated in the elastic gum warms the liquid and increases its solvent power, until at length the whole of the gum is dissolved. This operation is conducted on a somewhat extensive scale; for the iron vessel is large enough to contain more than half a ton of India-rubber, which requires three days of constant agitation for complete solution. The liquid thus produced has a consistency which fits it to be used as a varnish, or as a water-proofing medium, or as a cement, or for many other purposeswhich the sagacity and self-interest of manufacturers have enabled them to discover.

If we glance among the stores of the India-rubber manufacturers and retailers at the present day, we find the braids and cords, webs and bands, form no inconsiderable portion of the wares exposed for sale. These, in most cases, require that the India-rubber should be first made into blocks or cakes, next cut into sheets, and then separated into threads, or cords, or narrow strips. Supposing these preliminary cuttings to be effected, the making of braids and webs is exceedingly curious, for it involves a combination of the India-rubber with other materials. Let us briefly trace the processes. In the first place, the narrow cords are stretched by a kind of wheel, and kept extended till nearly deprived of their elasticity, and till they form a thread of the desired thickness. The thread is then put into a braiding machine which is a complicated and very ingenious apparatus, whereby a sheathing of cotton, silk, flax, or worsted, is wound round the India-rubber thread. In such a machine several threads are twisted round each other, from three to nearly thirty in number; each thread has its own bobbin, and all the bobbins revolve round a common centre, giving out their threads in the proportions and order required. Generally speaking, the braiding machine is employed in making stay-laces, braid, upholsterers’ cord, &c.; but it is also applicable to making the numerous elastic cords and webs which owe their elasticity to India-rubber.When an envelope of cotton, silk, flax, or worsted, has been given to the thread of India-rubber by the braiding machine, the threads are laid as warp in a loom, and woven into the required kind of web, whatever it may be. Then comes a curious development of the properties of the material; in the preliminary stretching, the India-rubber was made somewhat stiff and unyielding; but by now exposing it to the action of a hot smoothing iron upon a table, the elasticity is restored, the riband or web contracts in length, and the sheathing or envelope corrugates or wrinkles up on the surface. The web thus produced is very soft and elastic. The warp threads may be alternated with others of non-elastic character; and the weft-threads may be either elastic or non-elastic, so that any desired degree of elasticity may be obtained.

Why a piece of India-rubber, when it has been somewhat modified by heat and chemical action, should be deemed vulcanized, it is for the inventor to say. Let us take the name simply as an expression of a fact, that fire or heat has been brought to bear upon this substance as a means of affecting its qualities. The method was invented by Mr. Hancock seven or eight years ago, and it has been the means of giving a wide extension to the use of India-rubber.

This vulcanized India-rubber is in fact a compound of sulphur with the vegetable gum. When a sheet of India-rubber is immersed in liquid sulphur, amarked change takes place in its qualities; the sulphur acts upon the gum and combines with it; and indeed the two may almost be said to form a new substance. The methods by which the combination is brought about are varied, but the effect is in all cases very remarkable. The strength of the India-rubber is increased to an extraordinary degree. The elasticity is rendered more permanent, analogous in some respects to that of gutta-percha. The new substance will absorb essential oils without injury, whereas such oils would dissolve India-rubber. It retains its properties at a temperature so low that India-rubber would be too much hardened for use; and at a temperature so high that India-rubber would be destroyed. Later experimenters have found that antimony, and many other substances, may similarly be combined with India-rubber; and it is reasonable to expect that many useful novelties are in use for us in this “vulcanized” rubber.

Much ignorance exists in relation to the intrinsic merits of gutta-percha and India-rubber. It is generally supposed that there is so little difference that it is hardly perceptible, and that the one or the other may be used for the same purposes, with the same results. In order to correct this impression and convey an intelligent idea of their relative properties, we here give an analysis of the two gums:

Gutta-percha when immersed in boiling water contracts considerably in bulk, whilst India rubber, whenimmersed in boiling water, expands and very materially increases in bulk. Gutta-percha juice also is of a dark brown color, and consolidates in a few moments after exuding from the tree, when it becomes about as hard as wood. India-rubber sap, on the contrary, is perfectly white, and of about the consistency of thick cream; when it coagulates it gives from four to six parts water out of ten. Gutta-percha first treated with water, alcohol, and ether, and then dissolved with spirits of turpentine and precipitated, yields a substance consistent with the common properties of gutta-percha; but India-rubber similarly treated, results in a substance resembling in appearance the gum arabic. Gutta-percha by distillation yields 57⅔ per cent. of volatile matter; India-rubber by the same process, yields 85¾ per cent.

India-rubber, or caoutchouc, is produced from a milk-white sap taken chiefly from the Sephonca Cahuca tree, afterwards coagulated, and the whey pressed out or dried off by heat—the residue is the India-rubber of commerce.

Gutta-percha is produced from the Isonandra, or Gutta tree; is of a brownish color, and when exposed to air, soon solidifies, and forms the gutta-percha of commerce.

India-rubber of commerce, is of a soft, gummy nature, not very tenacious, and astonishingly elastic.

Gutta-percha of commerce is a fibrous material, much resembling the inner coating of white oak bark, is extremely tenacious, and without elasticity, or much flexibility.

India-rubber, when once reduced to a liquid stateby heat, appears like tar, and is unfit for further manufacture.

Gutta-percha may be melted and cooled any number of times, without injury for future manufacture.

India-rubber, by coming in contact with oil or other fatty substances, is soon decomposed and ruined for future use.

Gutta-percha is not injured by coming in contact with oil or other fatty substances—in fact one good use of it is for oil cans.

India-rubber is soon ruined for future use, if brought in contact with sulphuric, muriatic, and other acids.

Gutta-percha resists the action of sulphuric, muriatic, and nearly all other acids—in fact one great use of it is for acid vats, &c., and other vessels for holding acids.

India-rubber is a conductor of heat, cold and electricity.

Gutta-percha is a non-conductor of electricity, as well as of heat and cold.

India-rubber, in its crude state, when exposed to the action of boiling water, increases in bulk, does not lose its elastic properties, and cannot be moulded.

Gutta-percha, in its crude state, when exposed to the action of boiling water, contracts and becomes soft like dough or paste, and may then be moulded to any shape—which shape it will retain when cool.

India-rubber is vulcanized to reduce its elasticity and give it more firmness than is natural to the crude material.

India-rubber, vulcanized, is not so perfectly a repellent of water, as before being vulcanized.

India-rubber isnota perfect repellent of water, but is more or less absorbent, according to quality.

Gutta-percha has an exceedingly fine grain, and its oily property makes it aperfect repellentof liquids, oils, acids, and all oleaginous substances, so that when united to tanned leather, theoilin the leatherwill not affect the adhesive properties of the gutta-percha. Whereas oil in leatherwill decompose any India-rubbercement that may be applied to it.

Pure gutta-percha iswithoutsmell or disagreeable odor, and whenever it is found to produce any but a perfectly sweet odor, it arises from itsimpurities, and may be regarded as a test of its quality.

India-rubber when vulcanized has an odor about it very disagreeable. Itwill decompose, become sticky like tar, and much of it becomes entirely useless. It is vulcanized to reduce its elasticity and give it more firmness than is natural to the crude material, and when exposed to friction, even after vulcanization, it rolls up a dirty, sticky mass.

The foregoing analysis is so simple and clear, that the attentive reader will at once comprehend the natural as well as chemical differences existing in gutta-percha and India-rubber, being not only chemically, but mechanically and commercially different.

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