lt>6 ATTRACTION. 



read opposite to potassa 54.5, and to sulphuric acid 45.5, which is 

 the composition in 100 parts. 



Dr. Wollaston called oxygen 10. When this number was oppo- 

 site to oxygen, the other numbers, therefore, estimated by that scale, 

 represented " the combining weights of the bodies opposite to which 

 they may be found." " By mere inspection of this scale, we dis- 

 cover the quantity of one body which enters into combination with 

 another, the proportions of the elements of compounds, and the 

 quantities of these which enter into the composition of any particu- 

 lar weight of a compound ; the quantity of any substance required 

 to decompose a compound, by combining with either of its ingredi- 

 ents, and the quantity of the products that will be formed." The 

 progress of analysis has shewn that the numbers attached to Dr. Wol- 

 laston's scale are, in many instances, incorrect, but these errors have 

 been rectified in more recent editions of the scale,* in which, also, 

 the more convenient unit of hydrogen has been adopted. 



It is now ascertained that the foundations of chemical combination 

 are laid in mathematical relations, and the proportions of bodies have 

 therefore become subjects of mathematical calculation, as well as of 

 analytical experiment. The mathematical relations are proved by 

 analysis, to be true, and analysis is, in its turn, guided and corrected 

 by calculation. We may be assured that an analysis is wrong if it 

 does not correspond with numerical ratios, and we may predict that 

 the result will be expressed by one of a certain set of numbers, rela- 

 ted to each other by the same ratio, provided we are correctly ac- 

 quainted with any one combination of the same principles ; the new 

 compound of these principles will bear a relation to them which may 

 be expressed by whole numbers, although we cannot be certain 

 whether it will be double, triple, quadruple ; or a half, or a third, 

 or a fourth, &c. of the one known ; it will be certain, or in the 

 highest degree probable, that it will not be expressed by any inter- 

 mediate number. 



This beautiful discovery, as its foundations are laid in the exact 

 relations of quantity, places chemistry upon a mathematical basis. 



Mr. Higgins gave the first hint of this subject in 1788, in his view 

 of the phlogistic and anti-phlogistic theory, but Mr. Dalton first clear- 

 ly explained the doctrine. 



COMBINATION BY VOLUMES. 



(XX.) GASEOUS BODIES UNITE BY VOLUME, IN THE SIMPLE 

 RATIO OF 1 TO 1, 1 TO 2, 1 TO 3, 1 TO 4, &c. This law was es- 



* As by Mr. Reid, in Britain, and by Messrs. Henry and Beck, of the Rensselaer 

 School at Troy, N. Y., and by Dr. Barrat, at Middletown, Con. 



