Henry's Chemistry. 339 



portional numbers are those given by experiment, of which the 

 lowest ratio is one volume of hydrogen. But what must excite 

 peculiar astonishment in every individual who has studied with any 

 care the principles of reciprocal and multiple combination, is the 

 manner in which Dr. Henry here speaks of Gay-Lussac's theory 

 of volumes, which is, in trutl., a legitimate corollary from the 

 atomic theory itself. " In some instances, as in that of water, this 

 law (of gaseous volumes) is not inconsistent with the atomic theory; 

 but in other instances it cannot be reconciled with the relative weights 

 assigned to the atoms of certain elementary bodies. In nitrous gas, 

 for example, which Mr. Dalton conceives to be formed by the 

 union of one atom of oxygen with one atom of nitrogen, equal 

 volumes of these gases would give for the relative weights of oxy- 

 gen and nitrogen, numbers widely differing from those derived by 

 other methods. The too hypotheses of atoms, and of volumes, 

 cannot, therefore, both be true ; and f mm some well ascertained 

 exceptions to the latter, it appears to me that the theory of volumes 

 will scarcely be found tenable*.'" 



We really were astonished at this passage, in the ninth edition 

 of a book, of which the author says, " no pains has been spared 

 to render these volumes a. faithful abstract of the present state of 

 chemistry." It is an indisputable fact that nitrous gas is con- 

 stituted by the union of one volume of oxygen, and one volume of 

 nitrogen, which, retaining their total bulk after combination, afford 

 a compound gas, of mean specific gravity. It is another fact, equally 

 indisputable, that nitrous oxide is constituted by the union of two 

 volumes of nitrogen, and one of oxygen, which suffer a condensa- 

 tion equal to the volume of oxygen ; whence the gas has a cor- 

 responding increase of specific gravity. In the first, the com- 

 parison of the weights of equal volumes, gives the ratio of oxygen 

 to that of nitrogen as 16 to 14 ; or 2 atoms to i on Dr. Henry's 

 scale. In the second case, the same comparison gives the ratio of 

 8 to 14, or of 1 atom to 1, on the same scale. Here, therefore, is 

 a perfect accordance between the atomic hypothesis, and the theory 

 of \olumes. 



But to examine the hypothesis a little more minutely : Let us 

 assume a volume of oxygen so small as to contain only one atom ; 

 call its relative weight 16; then it will require for saturation, two 

 such volumes of hydrogen, whose weight will be 2. Next asr 

 sume a volume of nitrogen equal to the above volume of oxygen. 

 It will contain one atom, and have a relative weight of 14; 

 which will require for saturation three such volumes of hydrogen. 

 But three such volumes are impossible, because they imply the bi- 

 section of Mr. Dalton's radical and primary atom, which is absurd. 



The general fact of volumes requires no such mystifications, a$ 

 the Daltonian hypothesis docs. In saying so, we do not mean in 



Henry's Elem. 1 . 52. 

 Z2 



