tree, and in the following year an account of its preparation was given to the Academy.

The best time for obtaining the greatest quantity is in the rainy season, when the trees being pierced, a thick juice having neither taste nor smell exudes, which on its first appearance is of a yellowish white colour, and afterwards becomes darker by exposure to the atmosphere, and also solidified. Several coatings of the Caoutchouc being successively applied to the exterior surface of clay models of bottles, they are dried over fires, in the course of which each layer of Caoutchouc becomes blackened by the smoke. The lines usually visible on a bottle of India rubber are traced with a blunt tool. After being exposed to the drying effects of fire for a sufficient length of time, the clay is crushed, and shaken out of the bottles, which are then ready for exportation. The Indians had long been in the habit of making boots of Caoutchouc, which were perfectly waterproof; and the inhabitants of Quito were accustomed to employ it in the manufacture of cloth. Caoutchouc gives a soft and beautiful light, and before the demand in Europe became so great, the South Americans were in the

habit of employing it in flambeaux. One of these, an inch and a half in diameter, and two feet long, burns during twelve hours. The Caoutchouc obtained from India is prepared in a different manner from that which is followed in South America, being when imported in a solid flat state, and not blackened.

The elasticity of caoutchouc is its most remarkable property; pieces of it may be stretched, after being soaked in warm water, to seven or eight times their original length without being torn, or having their contractile power destroyed and bottles of it may, by means of a condensing syringe, be expanded to many times their original dimensions. If a bottle be soaked in well-washed sulphuric ether until quite soft, it may be inflated by means of the mouth until it has become so thin as to be transparent, and sufficiently light to ascend when filled with hydrogen gas. If dried in this state it will not again contract, and thin sheets of caoutchouc may thus be formed. A bottle has thus been expanded until it was six feet in diameter.

In æther caoutchouc readily dissolves, and on the evaporation of the æther, it remains unchanged

in any of its properties; this discovery was made after various experiments by Macquer and other eminent Frenchmen. The success was important as it enabled Macquer and others to transform it as occasion might require. Macquer used to make hollow tubes of caoutchouc by coating a stick or cylinder of wax with his new solution, and when the proper thickness was attained, by plunging the whole into hot water, the wax was melted and flowed out of the tube. In a similar way Frederick the Great of Prussia had a pair of Indiarubber boots made; a cast of his leg was taken in clay, and then coated with the solution, after which the clay was broken and taken out piecemeal, leaving a pair of well-shaped, seamless, water-proof boots. The great expense of using æther prevented this process from being carried to any great extent, and various attempts were made to render the tough caoutchouc as it was imported, capable of being changed in form. But about twenty-four years ago a mode of employing India-rubber was devised, and a patent taken out for it. It was discovered that coal-oil was a perfect solvent for caoutchouc, and an immediate application of it to that purpose was made.

Coal-oil used previously to be thrown away as of no value, and could therefore be purchased at a cheap rate. After it is dissolved in coal-oil, the caoutchouc is spread upon the surface of a piece of cloth, upon which a similar piece is then extended, and the whole passed between a pair of rollers. Thus the fabric consists of two pieces of cloth with a layer of caoutchouc between them, and uniting them together. The cloth thus prepared is so impervious to moisture and to air, that hydrostatic or floating beds for invalids are formed of it, and even beds and cushions are rendered elastic by inflating them.

The balloon in which Mr. Green the aeronaut ascended on the day of the coronation of George the Fourth, in 1821, was made of double silk, cemented together by caoutchouc dissolved in oil of turpentine by a peculiar process; the balloon from falling into the sea was rendered unfit for further use, but the silk was cut up, and used as waterproof cloaks, &c., by different persons for several years. Caoutchouc in its solid form is very valuable for many surgical instruments. There are many delicate operations in surgery, in which great elasticity in the instrument is required at the

same time that a capability of resisting fluids is necessary. Caoutchouc is fitted for this in both ways, for if soaked for a short time in warm water, it may be stretched to seven or eight times its natural length, and it will resist the action of watery, spirituous, saline, acid, and oily fluids. The juice, which is called by the natives Hhvé, as it exudes from the tree, is a little heavier than water, but when it has become dry it is a little lighter. Caoutchouc is used in the manufacture of numerous articles for which elasticity renders it adapted. It is also cut by machinery with great rapidity into very fine thread, to which a still greater degree of tenuity is given by stretching it as it is wound tightly upon bobbins, where it is allowed to remain till its contractile power be lost

This thread is woven into web, and into a variety of ornaments. The fabric of caoutchouc web was commenced at Vienna, but much improved and extended in the manufactory at St. Denis, near Paris, in which there are about fifteen hundred of the machines for plaiting the thread around the filaments of the elastic gum, and all the other departments in correspondent proportion. The web in its formation undergoes no less than