530 INDUCTION. 



commenced by Bichat, and carried on by subsequent biologists, 

 of the properties of the bodily organs, to the elementary 

 properties of the tissues into which they are anatomically 

 decomposed. 



Another striking instance is afforded by Dalton's gene- 

 ralization, commonly known as the atomic theory. It had 

 been known from the very commencement of accurate chemical 

 observation, that any two bodies combine chemically with 

 one another in only a certain number of proportions; but 

 those proportions were in each case expressed by a percentage 

 1 so many parts (by weight) of each ingredient, in 100 of the 

 compound; (say 35 and a fraction of one element, 64 and a 

 fraction of the other) : in which mode of statement no relation 

 was perceived between the proportion in which a given element 

 combines with one substance, and that in which it combines 

 with others. The great step made by Dalton consisted in per- 

 ceiving, that a unit of weight might be established for each 

 substance, such that by supposing the substance to enter into 

 all its combinations in the ratio either of that unit, or of some 

 low multiple of that unit, all the different proportions, previously 

 expressed by percentages, were found to result. Thus 1 being 

 assumed as the unit of hydrogen, if 8 were then taken as that 

 of oxygen, the combination of one unit of hydrogen with one 

 unit of oxygen would produce the exact proportion of weight 

 between the two substances which is known to exist in water ; 

 the combination of one unit of hydrogen with two units of 

 oxygen would produce the proportion which exists in the other 

 compound of the same two elements, called peroxide of 

 hydrogen ; and the combinations of hydrogen and of oxygen 

 with all other substances, would correspond with the suppo- 

 sition that those elements enter into combination by single 

 units, or twos, or threes, of the numbers assigned to them, 

 1 and 8, and the other substances by ones or twos or threes 

 of other determinate numbers proper to each. The result is 

 that a table of the equivalent numbers, or, as they are called, 

 atomic weights, of all the elementary substances, comprises in 

 itself, and scientifically explains, all the proportions in which 

 any substance, elementary or compound, is found capable of 



