PREFACE. 



was from the elastic force of the latent caloric 

 that belongs to nitre, sulphur, and charcoal, 

 that man, unconsciously, obtained the power of 

 gunpowder ; the invention of which has essen- 

 tially modified the condition of the human race : 

 for it thenceforward secured the uninterrupted 

 progress of civilization, which can never again 

 be arrested by the incursions of barbarous 

 hordes, nor the light of knowledge be extin- 

 guished in embryo, as during the early periods 

 of history. It was by discovering that a piece 

 of metal called the loadstone, when horizon- 

 tally balanced on a pivot, is constantly directed 

 to certain points in the polar regions, that 

 commerce and civilization have been extended 

 to the remotest parts of the earth. But men 

 have yet to learn that the same principle 

 which directs the compass-needle to the poles, 

 guides the planets in their orbits, and fills 

 them with life. 



It was by seizing the grand lever of nature 

 as a moving agent, that man was enabled 

 to create the steam-engine, which has brought 

 about a more important revolution in the con- 

 dition of nations, than all the united discoveries 

 of antiquity for thousands of years. Nor can 

 there be a reasonable doubt that a complete 



