338 THE POPULAR SCIENCE MONTHLY. 



beneficial effects to mankind, it may be said, like mercy, to shed its 

 gentle dews from heaven ; and, by being the prime cause of annihilat- 

 ing distances, it has brought the human race closer together, and is 

 thus the " one touch of nature that makes the whole world kin." 



It is not only the most useful but it is the most valuable of all min- 

 erals, on account of the wealth that is produced through its agency. 

 It is well understood that money is a sequence of work, and a com- 

 munity that has small labor-bills can take the trade away from those 

 that have to pay high rates. Let us, therefore, see what work this sub- 

 stance can produce. 



In mechanics the unit of work is the power necessary to raise one 

 pound one foot high, and this is known as a foot-pound. From numer- 

 ous experiments and observations, an able-bodied man, in working ten 

 hours a day, exerts an average force of 1,000,000 foot-pounds. "When 

 coal is burned under a boiler it produces steam, which in turn pro- 

 duces work as it drives machinery. Therefore, coal produces work, 

 the amount of which will vary according to the perfection of the ma- 

 chinery and the appliances for generating the steam. If we take an 

 average of all kinds of engines, one pound of coal will produce steam 

 sufficient to exercise a power of 500,000 foot-pounds. Hence the work 

 accomplished by two pounds of the fuel equals a man's day's work. 

 Now, mark the surprising results to which this leads us. The popula- 

 tion of the United States is about 40,000,000, and in 1877 we produced 

 50,000,000 tons of coal. If one-fourth of this were applied to manu- 

 facturing, etc., it would do as much work as our whole population, as- 

 suming them all to be able-bodied men, in 350 days. The coal at the 

 engine will average about four dollars a ton, while the price of unskilled 

 manual labor can be put down at one dollar a day. Applying these fig- 

 ures, we see that the work in the first case would have cost 150,000,000 ; 

 while in the latter, were it even possible to employ so many men, the 

 labor-bill would have been $14,000,000,000 ! Can any one for a moment 

 question the advantage or the value of the substance ? 



In these days, accustomed as we are to its multitudinous uses, it is 

 difficult to imagine ourselves in the position of the early writers, who 

 touched with uncertain pen on what they thought to be the leading 

 characters of a rare and ambiguous mineral, or to conceive that its in- 

 troduction was accompanied by such prejudice and superstition that 

 laws were actually passed forbidding its use by the very countries that 

 now consider it as the greatest of their possessions. In fact, it is of 

 comparatively late date that it has sprung into the important position 

 which it i^ow occupies. 



The earliest express mention made of it as a fuel was about 300 b. c, 

 in the writings of Theophrastus, the pupil of Aristotle, who speaks of 

 it as being found in Liguria (now the province of Genoa) and in Elis 

 on the way to Olympias, where it was used by smiths. Ampelitis, a 

 black stone "like bitumen," is mentioned by Pliny as available for 



