The substance of which the silk is formed, is a fine yellow transparent gum, contained in two reservoirs that wind about the intestines, and which, when they are unfolded, are about ten inches long; they terminate in two exceeding small orifices near the mouth, through which the silk is drawn, or spun to the degree of fineness which its occasions may require. This apparatus has been compared to the instrument used by wire-drawers, and by which gold and silver is drawn to any degree of minuteness. From each of these reservoirs proceeds a thread, which are united afterwards; so that if it be examined by the microscope, it will be found to consist of two cylinders or threads glued together, with a groove in the middle; a separation may sometimes be perceived. When the silk-worm has found a convenient situation, it sets to work, first spinning some random threads, which serve to support the future superstructure; upon these it forms an oval of a loose texture, consisting of what is called the floss-silk; within this it forms a firm and more consistent ball of silk, remaining during the whole business within the circumference of the spheroid that it is forming, resting on its hinder parts, and with its mouth and fore legs directing and fastening the threads. These threads are not directed in a regular circular form, but are spun in different spots, in an infinite number of zig-zag lines; so that when it is wound off, it proceeds in a very irregular manner, sometimes from one side of the cone, then from the other. This thread, when measured, has been found to be about three-hundred yards long, and so fine, that eight or ten are generally rolled off into one by the manufacturers. The silk-worm usually employs about three days in finishing this cone; the inside is generally smeared with a kind of gum, that is designed to keep out the rain: in this cone it assumes the pupa form, and remains therein from fifteen to thirty days, according to the warmth of the climate. When the moth is formed, it moistens the end of this cone, and by frequent motions of the head loosens the texture of the silk, so as to form a hole without breaking it. When the silk-worm has acquired its perfect growth, the reservoirs of silk are full, and it is pressed by its sensations to get rid of this incumbrance, and accordingly spins a cone, the altitude and size of which are proportioned to its wants: by traversing backwards and forwards, it is relieved, and attains by an innate desire the end for which it was formed; and thus a caterpillar, whose form is rather disgusting to the human unphilosophic eye, becomes a considerable object of manufacture and trade, a source of wealth, and, from the extensive employment it affords, a blessing to thousands. The size of the cone is not always proportioned to that of the caterpillar; some that are small construct larger cones than others which exceed them in bulk.