r 



ON MR. DALTON's PRINCIPLE OF COMBINATION. fiSJ 



is described, and an outline is given of their chemical and 

 physical properties, but nothing occurs, either in the way of 

 proof or illustration of the ** general conclusions." We, 

 however, naturally expect, that we shall find the informatioti 

 ef which we are in search, when we come to the next chapter, 

 which professedly treats of compounds of two elements, and Compounds of 

 first of water. After giving a brief account of the ex peri- ^°^^^"^*" ^* 

 inents on the composition and decomposition of water, ex- 

 periments which have been repeated in various forms, by 

 the most distinguished chemists of France and England, 

 and respecting which the utmost pains have been taken 

 to ensure accuracy, Mr. Dalton remarks, that " the 

 •' general result was that 85 parts by weight of oxi- 

 " gen unite to 15 of hidrogen to form water." Tfi 

 this estimate, however, he does not acquiesce; he refers 

 to some objections that have been urged against it by Mr. 

 Humboldt and Gay-Lussac, whose reasoning on this sub- 

 ject he considers as *' perfectly satisfactory," They con- 

 ceive, that in consequence of the aqueous vapour which 

 gasscs usually contain, a less quantity of real hidrogen mu&t 

 have been en) ployed, than was assumed in the calculations, 

 and they reduce it from 15 parts to 14'3 parts, increasing, 

 of course, the quantity of pure oxigen to 85*7. Mr, Dalton 

 adds, " the relation of these numbers is that of 7 to 1 

 nearly." He continues; "There is another consideration 

 *' which seems to put this matter beyond doubt. In Vol- 

 " ta's eudiometer, two measures of hidrogen require just 

 ** one of oxigen to saturate them. Now, the accurate expe- 

 ** riments of Cavendish and Lavoisier have shown, that 

 " oxigen is nearly 14 times the weight of hidrogen ; the ex- 

 ** act coincidence of this w th the conclusion above deduced 

 " is a sufficient confirmation." Notwithbtauding the ac- 

 knowledged sagacity of the author, I cannot but consider 

 the above lemarks as totally irrelevant to the question under 

 discussion. The facts that are adduced refer merely to the 

 relation which the bulk of hidrogenous gas bears to its spe- 

 cilic gravity, and have no relation to either of the fundamen«» 

 tal points in Mr. Dalton's hypothesis. 



Haymg now gone through the chaj^ter i.i \\h ch the pro- ^Y\^ ^.j^f.^^ ^ 

 mi-jed facts and experiments are contained, it may be proper aot sip^o t 



to 



