164 Analysis of Scientific Books. 



rine," &c. " Five of them, have their specific gravity, equal 

 to one fourth the weight of their atoms. These are hydriodic 

 acid, muriatic acid, deutoxide of azote, hydrocyanic acid, and 

 ammonia. It follows as a consequence from the preceding 

 facts, that the number of atoms in a given volume of these 3 

 sets of gases, are to each other, as the following numbers : 



First set 4 



Second set 2 



Third set 1*" 



We ask Dr. Thomson, " Do you think Aristotle right, when 

 he says that relatives are related ? Do you judge the analy- 

 tical investigation of the first part of your enthymen, deficient, 

 secundum quoad, or quoad minus?" Against his first grand 

 proposition, that if we assume the specific gravity of oxygen to 

 be 1, and the weight of its atom to be 1, then " there is one 

 body whose specific gravity is equal to the weight of its atom," 

 we have nothing very forcible to urge, but only to congratulate 

 him on this instance of invention. The enigmatic empiricism 

 of his following propositions, may deserve a little developement. 

 As in the Daltonian hypothesis, which Dr. Thomson has long 

 laboured to expound, the atomic unit is half a volume of 

 oxygen ; so, in order to convert the atomic relations of other 

 bodies, into relations by volumie, we must multiply their 

 atomic weight, by that of half a volume of oxygen gas, which 

 is 0.5555, when atmospheric air is called 1.; but 0.5 of course, 

 if oxygen gas be assumed as the standard of gaseous density, 

 or 1 . Specific gravity is merely the relative weight of equal 

 volumes of matter. If oxygen be, therefore, taken as the 

 standard to which both atomic weight, and weight of volume is 

 referred, other volumes will become =: one half of their atomic 

 weights, or = atom x 0.5, instead of = atom x 0.5555. In 

 this hypothesis, 2 volumes of hydrogen form unity. But if 

 one volume of hydrogen come to be accounted unity in any case, 

 as we must consider it to be with regard to muriatic, hydriodic, 

 and hydrocyanic acids, as well as ammonia, then the volumes, 

 or specific gravities, will become =: atom x 0.25, instead of 

 atom X 0.5 as in the second case, or atom x 0.555, as in the 

 common reduction to atmospheric air. And as to deutoxide of 

 azote, one volume of it contains only half a volume of oxygen, 

 and is therefore equivalent to a single volume of hydrogen, or 



0.5 

 half tlie Daltonian unit of volume, = -^ , in the above case. 



So that Dr. Thomson's tabular distinctions are merely dif- 

 ferent aspects of his atomic Proteus, which he mistakes for 

 the different aspects of nature, and holds out to his readers as 

 essential distinctions in the constitution of things. 



* Si/atem, III. 25. 



