6 1 4 THE POPULAR SCIENCE MONTHLY. 



square, it will require 240 tons ; if three inches square, it will scarcely 

 break with 540 tons. Bars of steel are not often made larger than this, 

 although Krupp, in his colossal works, doubtless makes some whose 

 section equals 144 square inches. To pull apart such a bar would 

 require a strain equal to the weight of 8,640 tons. It requires an 

 effort to grasp the meaning of such a load. A stout team will haul 

 two tons over a good road for a moderate distance ; that number of 

 tons would require more than 4,000 such teams to move it. If put 

 upon a railroad it would need 864 cars and twenty-three locomotives 

 to draw it. It would equal in weight one of the largest ocean-steam- 

 ers with its complement of freight. 



But we shall need a much larger unit than this. Could a bar of 

 steel three feet square be forged and, judging from the size of his 

 steel cannon, Krupp might do this also it would be able to lift nine 

 times that great amount. Probably no furnace can much exceed this, 



but we may imagine a monster bar measuring one rod 16 feet 



square, and by easy multiplication we find its strength great enough 

 to lift 30| times as much as the last, or in figures 2,352,240 tons, three 

 times the weight of the cotton crop of the United States when it 

 equaled 4,000,000 bales. 



To get a fit unit for our purpose we shall need to go far beyond 

 this, but first pause to contemplate a bar of steel 16|- feet square. 

 As it lay stretched upon the ground, we would need a ladder to get 

 upon its upper side. Few rooms in private dwellings are 16 feet 

 high, and 164 feet wide makes a spacious parlor. 



Endeavor to get some idea of its tenacity, and how many million 

 horses it would require to pull it asunder, and then, after getting some- 

 what accustomed to the greatness and strength of a bar of solid steel 

 16 feet square, imagine one which is one mile square 5,280 feet 

 wide, and as many thick. If it lay on the ground near the Catskill 

 Mountains, its upper surface would overtop their highest summit by 

 more than 1,000 feet. It would be equal to 102,400 such monster bars 

 as the last. Its lifting power would be nearly 240,869,000,000 tons. 

 The mind is utterly unable to grasp such figures. The whole globe 

 contains 1,200,000,000 inhabitants. If each man, woman, and child, 

 could pull with a force of 100 pounds a large estimate to move such 

 a weight would require the united efforts of the inhabitants of two 

 thousand such worlds as this. 



As I shall have frequent occasion to speak of the load which such 

 a bar could sustain, I shall, for convenience, call it in round numbers 

 240,000,000,000 tons, neglecting the other figures, because the num- 

 ber is so inconceivably great that taking from it a billion or so of tons 

 will alter the result less than one half of one per cent. This bar is to 

 be the unit of measure which I shall for the present employ, and with 

 its help I shall attempt to give some idea of the influence of the sun 

 in holding the system together, and of the attraction exerted by the 



