Page:Popular Science Monthly Volume 55.djvu/443

Rh E. D. Bell and appeared in Nature for March 23d. The table was made for the purpose of demonstrating a constant relation (in length) between these two periods of life, which the author expresses in the following formula, in which f. t. l. = full term of life, and p. m. the time required to arrive at maturity:

and which seems to be fairly well borne out by the table:

The Manufacture of Firecrackers in China.—There were exported from China during the year ending June 30, 1897, 26,705,733 pounds of firecrackers, all from the province of Kwantung. The exports, however, represent only a small portion of the number manufactured, as the use of the cracker is universal all over China. They are used at weddings, births, funerals, at festivals, religious and civil, and in fact on all occasions out of the ordinary routine. The United States consul general at Shanghai gives the following, account of the industry: There are no large factories; the crackers are made in small houses and in the shops where they are sold. In making them only the cheapest kind of straw paper is used for the body of the cracker. A little finer paper is used for the wrapper. A piece of straw paper, nine by thirty inches, will make twenty-one crackers an inch and a half long and a quarter inch in diameter. The powder is also of the cheapest grade, and is made in the locality where used. It costs about six cents per pound. For the fuse a paper (called "leather" in Shanghai) is used, which is imported from Japan, and is made from the inner lining of the bamboo. In other places a fine rice paper is used, generally stiffened slightly with buckwheat-flour paste, which the Chinese say adds to its inflammability. A strip of this paper one third of an inch wide by fourteen inches (a Chinese foot) long is laid on a table, and a very little powder put down the middle of it with a hollow bamboo stick. A quick twist of the paper makes the fuse ready for use. The straw paper is first rolled by hand around an iron rod, which varies in size according to the size of cracker to be made. To complete the rolling a rude machine is used. This consists of two uprights supporting an axis from which is suspended, by two arms, a heavy piece of wood, slightly convex on the lower side. There is just room between this swinging block and top of the table to place the cracker. As each layer of paper is put on by hand, the cracker is placed on the table and the suspended weight is drawn over the roll, thus tightening it until no more can be passed under the weight. For the smallest "whip" crackers, the workman uses for compression, instead of this machine, a heavy piece of wood fitted with a handle like that of a carpenter's plane. In filling crackers, two hundred to three hundred are tightly tied together in a bunch; red clay is spread over the end of the bunch, and forced into the end of each cracker with a punch. While the clay is being treated a little water is sprayed on it, which makes it pack closer. The powder is poured in at the other end of the cracker. With the aid of an awl the edge of the paper is turned in at the upper end of the cracker, and the fuse is inserted through this. The long ends of the fuses are braided together in such a way that the crackers lie in two parallel rows.