644 TIIE POPULAR SCIENCE MONTHLY. 



elusive source of this energy was muscular force, derived from com- 

 pulsory human labor; and all the monuments and objects that have 

 been left to us, as marks of ancient civilization, are the results of 

 organized systems of slavery. The rock-sculptures of Elephanta, the 

 Pyramids of Egypt, and the temples of Greece, were all the result of 

 the labor of slaves, directed by the minds of freemen. It is said that a 

 hundred thousand slaves were employed at one time in the construc- 

 tion of the Pyramids of Egypt ; one hundred and twenty thousand 

 were engaged in hewing the obelisks of Thebes, and an equal num- 

 ber in digging the ancient canal which joined the Nile and the Red 

 Sea. These slaves were treated as beasts of burden, or as mere ma- 

 chines, of which Athens, in her palmy days, had four hundred thou- 

 sand, with but twenty thousand freemen. 



Now, we owe the abolition of this condition of humanity, in the 

 higher civilized nations of the world at the present day, to the study 

 of the laws of the operations of Nature. By a knowledge of these 

 laws the energies of the elements of Nature are substituted for hu- 

 man labor, and by this substitution mankind is not only relieved 

 from brute-labor, but also given control of energies which enable 

 him to produce effects which could only result from the muscular 

 power of beings of a superior order. It may be shown by a simple 

 calculation that about fifteen tons of anthracite coal burned in the 

 furnace of one of our best steam-engines exerts an energy equal to that 

 of an able-bodied slave, working ten hours a day for thirty years of his 

 active life. It is this substitution of the energies of Nature for the 

 power of human muscle that, as we have said, has abolished sla- 

 very and elevated humanity to a higher plane than was ever dreamed 

 of by the wisest sages of ancient times. To illustrate this, a few 

 examples will suffice. As one of these, we may refer to the progress 

 of the arts of locomotion, and the means which science has afforded 

 for the instantaneous interchange of thought between men in the 

 most distant parts of the earth ; as another, to the production of 

 clothing fabrics, in which a single individual, directing the energies 

 of an engine of one-man power, is capable of doing three thousand 

 times the work of an ordinary weaver. As a third example, we may 

 point to the art of printing by means of the steam-press, in which a 

 single man will make more copies in a given time of a composition, 

 than a million of ancient transcribers could do. Science is every day 

 creating new arts, and modifying and improving the processes of old 

 ones. We are skeptical as regards the value of lost arts. It is true 

 there are arts which have fallen into disuse, and others which de- 

 pend upon the skill and patience of the individual, but none, which 

 rests on any lost secret of Nature which science cannot restore. 



The results we have mentioned are frequently attributed by super- 

 ficial observation to immediate practical invention of persons having 

 little or no knowledge of abstract science. But, in regard to this, it 



