130 The Evolution of Chemistry. 



pound would be apt to require thirty-two ounces to com- 

 plete the second form of saturation. The amount of the 

 substance to be saturated would be the same in both cases. 

 Where there were three such, the third would require three 

 times sixteen, or forty-eight ounces. The unions in every 

 chemical bond were found to be in definite and multiple 

 proportions. On looking around for an explanation of this 

 curious fact, he found himself compelled to adopt the idea 

 that every body is composed of a great number of like dis- 

 crete parts, and that all these parts in the same substance 

 have the same size and weight. A solid body is thus con- 

 ceived to be like an army of soldiers, where weight and 

 height are regulated by statute. Supposing the army con- 

 tains two thousand, and an army of amazons comes along 

 of the same number. If every soldier marries an amazon 

 we are thus able to see why a given weight of male army 

 always matches a corresponding, though perhaps lower, 

 weight of the female one. The weight of the army is the 

 sum of the weight of its individual units. If every amazon 

 has a mother with her or every soldier a father with him, 

 then every one of one side will take two of the other. In 

 such a case, double the weight of one side would be needed 

 and multiple proportions shown. If every soldier took into 

 the union a father and a brother, then three times the 

 weight of male army would be needed to supply one weight 

 of amazon. Dalton's explanation is called the atomic theory, 

 and the ultimate parts of a substance bear the name " atom." 

 Two thousand five hundred years ago Leucippos undertook 

 to explain facts then known by a somewhat similar theory. 

 In 450 B. c. Democritus renewed the same, while still later 

 Epicurus gave it a fuller development. The Epicurean 

 philosophy was set forth by Lucretius in a poem written a 

 little over half a century before Christ. The Epicureans 

 were bitterly opposed to the school of Aristotle, but during 

 the dark ages they were practically annihilated by the fol- 

 lowers of the latter. In 1592 Gassendi undertook to re- 

 habilitate the atomic theory, but failed to gain a following. 

 Sir Isaac Newton saw in the atomic theory a possible ex- 

 planation of gravity. From Newton to Dalton nothing was 

 done to advance this hypothesis. 



Either matter is continuous, as it seems to be to carnal 

 sense, or else it is discrete and therefore atomic. There is 

 no third alternative. The followers of Aristotle chose one 

 side and those of Epicurus the other. One must be right. 



