Inventions in the Century

by William Henry Doolittle

We have already had occasion to refer to Tilghman’s sand blast in describing pneumatic apparatus. In glass manufacture the process is used in etching on glass designs of every kind, both simple and intricate. The sand forced by steam, or by compressed air on the exposed portions of the glass on which the design rests, will cut the same deeply, or most delicately, as the hand and eye of the operator may direct.

Machines.—In addition to the new styles of furnaces, moulds and melting, and rolling mills to which we have alluded, mention may be made of annealing and cooling ovens, by which latter the glass is greatly improved by being allowed to gradually cool. A large number of instruments have been invented for special purposes, such as for making the beautiful expensive cut glass, which is flint glass ground by wheels of iron, stone, and emery into the desired designs, while water is being applied, and then polished by wheels of wood, and pumice, or rottenstone; for grinding and polishing glass for lenses; and for polishing and finishing plate glass; for applying glass lining to metal pipes, tubes, etc.; for the delicate engraving of glass by small revolving copper disks, varying in size from the diameter of a cent down to one-fifteenth of an inch, cutting the finest blade of grass, a tiny bud, the downy wing of an insect, or the faint shadow of an exquisite eyebrow.

Cameo cutting and incrustation; porcelain electroplating and moulding apparatus, and apparatus for making porcelain plates before drying and burning, may be added to the list.

It would be a much longer list to enumerate the various objects made of glass unknown or not in common use in former generations. The reader must call to mind or imagine any article which he thinks desirable to be made from or covered with this lustrous indestructible material, or any practicable form of instrument for the transmission of light, and it is quite likely he will find it already at hand in shops or instruments in factories ready for its making.

Rubber—Goodyear.

The rubber tree, whether in India with its immense trunk towering above all its fellows and wearing a lofty crown, hundreds of feet in circumference, of mixed green and yellow blossoms; or in South America, more slender and shorter but still beautiful in clustered leaves and flowers on its long, loosely pendent branches; or in Africa, still more slender and growing as a giant creeper upon the highest trees along the water courses, hiding its struggling support and festooning the whole forest with its glossy dark green leaves, sweetly scented, pure white, star-like flowers, and its orange-like fruit—yields from its veins a milk which man has converted into one of the most useful articles of the century.

The modes of treating this milky juice varies among the natives of the several countries where the trees abound. In Africa they cut or strip the bark, and as the milk oozes out the natives catch and smear it thickly over their limbs and bodies, and when it dries pull it off and cut it into blocks for transportation. In Brazil the juice is collected in clay vessels and smoked and dried in a smouldering fire of palm nuts, which gives the material its dark brown appearance. They mould the softened rubber over clay patterns in the form of shoes, jars, vases, tubes, etc., and as they are sticky they carry them separated on poles to the large towns and sea ports and sell them in this condition. It was some such articles that first attracted the attention of Europeans, who during the eighteenth century called the attention of their countrymen to them.

It was in 1736 that La Condamine described rubber to the French Academy. He afterward resided in the valley of the Amazon ten years, and then he and MM. Herissent, Macquer, and Grossat, again by their writings and experiments interested the scientific and commercial world in the matter.

In 1770 Dr. Priestley published the fact that this rubber had become notable for rubbing out pencil marks, bits of it being sold for a high price for that purpose. About 1797, some Englishman began to make water-proof varnish from it, and to take out patents for the same. This was as far as the art had advanced in caoutchouc, or rubber, in the eighteenth century.

In 1819 Mr. Mackintosh, of Glasgow, began experimenting with the oil of naphtha obtained from gas works as a solvent for India rubber; and so successfully that he made a water-proof varnish which was applied to fabrics, took out his patent in England in 1823, and thus was started the celebrated “Mackintoshes.”