466 THE POPULAR SCIENCE MONTHLY. 



can be fully appreciated. Such a furnace will have passed through 

 it in twenty-four hours the following materials : 



Ore 1,263,360 pounds or 564 gross tons. 



Coke 990,384 " " 442 " " 



Limestone 353,741 " " 158 " " 



Atmospheric air (blast) 2,331,840 " "1,041 " " 



Totals 4,939,325 " "2,205 " " 



which is equal to ninety -two tons per hour, or 1'53 tons per min- 

 ute.* 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,GG6 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 tuyeres, each seven inches in diameter, this torrid air would 

 rush through each tuyere (under a pressure of nine pounds per 

 square inch) at the rate of 12,143 cubic feet, and having the enor- 

 mous 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. 



[To be continued.] 



A contribution has been made to the speculations respecting the relative 

 growth of the white and colored population of the United States by Quarter- 

 master-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. 



* Perhaps the volume of materials required in the manufacture of pig iron may be more 

 readily comprehended by considering that, for the making of a pound of that commodity 

 from the best ore, there are required 1612 pounds of ore; 0*786 pound of coke; 0*451 

 pound of limestone ; 2*977 pounds of air, or a total of 5*876 pounds of materials for each 

 pound of iron produced. 



