Page:On the economy of machinery and manufactures - Babbage - 1846.djvu/145

Rh them, made entirely by caterpillars. The following is the mode of proceeding adopted:—He makes a paste of the leaves of the plant, which is the usual food of the species of caterpillar he employs, and spreads it thinly over a stone, or other flat substance. He then, with a camel-hair pencil dipped in olive oil, draws upon the coating of paste the pattern he wishes the insects to leave open. This stone is then placed in an inclined position, and a number of the caterpillars are placed at the bottom. A peculiar species is chosen, which spins a strong web; and the animals commencing at the bottom, eat and spin their way up to the top, carefully avoiding every part touched by the oil, but devouring all the rest of the paste. The extreme lightness of these veils, combined with some strength, is truly surprising. One of them, measuring twenty-six and a half inches by seventeen inches, weighed only 1.51 grains; a degree of lightness which will appear more strongly by contrast with other fabrics. One square yard of the substance of which these veils are made weighs 4 grains, whilst one square yard of silk gauze weighs 137 grains, and one square yard of the finest patent net weighs 262 grains. The ladies' coloured muslin dresses, mentioned in the table sub-joined, cost ten shillings per dress, and each weigh six ounces; the cotton from which they are made weighing nearly six and two-ninth ounces avoirdupois weight.