Page:Popular Science Monthly Volume 38.djvu/482

466 can be fully appreciated. Such a furnace will have passed through it in twenty-four hours the following materials:

which is equal to ninety-two tons per hour, or 1·53 tons per minute. From this quantity of materials there will be produced in twenty-four hours 784,000 pounds or 350 gross tons of pig iron, which is at the rate of 32,666 pounds or 14·57 tons per hour, or 544 pounds per minute.

Heating the 25,000 cubic feet of air supplied per minute to a, temperature of 1,200 Fahr., its volume would be increased to 85,000 cubic feet; and, on the supposition that the furnace is blown by seven tuyères, each seven inches in diameter, this torrid air would rush through each tuyère (under a pressure of nine pounds per square inch) at the rate of 12,143 cubic feet, and having the enormous lineal velocity of 45,417 feet per minute. This velocity is over five times that of the most violent tornadoes, and the pressure is more than twenty-five times greater. Should a blast of equal pressure and velocity come from unfathomed space and envelop this earth, it is absolutely certain that no living beings or loose materials would be left upon its rock-ribbed skeleton, which, stripped of its flesh and blood, fields and forests, lakes and oceans, would be hurled into a new orbit and made to assume revolutions and rotations whose amplitude and duration it is impossible to imagine or describe.

has been made to the speculations respecting the relative growth of the white and colored population of the United States by Quartermaster-General Meigs, who has published tables exhibiting the increase of both, by decades, since 1790. They show that the total population had increased eight-fold in 1860; while the average increase of whites by decades was 32·8 per cent, and of negroes 26·8 per cent. In 1790, there were 3,172,000 more whites than negroes; in 1880, 48,575,000; in 1890, probably 58,640,000 more; and if the present relative rates of increase are maintained, there will be, in 1990, 1,067,043,000 more. The estimate should set the apprehension of negro supremacy a considerable distance away.