ON -iiiR. Walton's principle of combination. OT3 



to combine, their atoms must unite in the following order, 



ijeginninj^ with the most simple case. 



*' 1 atom of A + 1 atom of B zi 1 atom of C, binary. 

 " 1 atom of A 4- 2 atomsoFB n I atom of D, ternary, 

 " 'iaiomsof A + J atom ofB = 1 atom of E, ternary. 

 ** I atom of A + 3 atoms of B :r 1 atom of F, quaternary, 

 ** 3 atomsof A + 1 atom of B iz 1 atom of G, quaternary. 



The author then proceeds to lay down some '* general 

 rules," which, not being immediately deducible from the 

 foregoing statement, nor, as far aa I can j'udge, having any 

 previous analogies in their'favour, we must regard as specu- 

 lative positions, the proof of which is reserved for the 2nd 

 part of the work. The first four of these rules areas follows* 

 ** 1st. When only one combination of two bodies can be 

 " obtained, it must be presumed to be a binary one, unless 

 ** some cause appear to the contrary. 2nd. When two cora- 

 *' biiiations are observed, they must be presumed to be a^ 

 ^' binarr/'dn&ii tefnary, 3d. When three combinations are 

 " obtained. We rriay expect one to be binary, and the other 

 ** two /miary. '4lb. When four cbmbiuatiohs dre observed, 

 ** we should expect one binary, two ternary, and one qua- 

 *• ternary, &c." In support of these positions Mr. Dalton 

 offers no arguments, but resting their truth entirely upon 

 their intrinsic probability, he proceeds, without any hesita- 

 tion, to deduce from them the most important conclusions, 

 and such as lie at the foupdation of a great part' of his sub- 

 sequent reasoning. 



From the first of the above rules Mr. Dalton draws the Composition 



two conclusions, that water is a binary compound of hidro* *'^^'*^^''' ^^^ 



, , , . • , /, . ofamnioiua. 



gen and oxigen, having the relative weight ot its two ele- 

 mentary atoms ideaiiy as 1 to 7 ; and that ammonia is a 

 binary compound of azote and oxigen, the atoms of which 

 have the weight of 1 to 5 respectively. But befpre we can 

 follow Mr. Dalton through this train of consequences, there 

 are some difficulties to be cleared up, which oppose our pro- 

 gress at the very outset. When bodies unite only in one pro- 

 portion, whence do we learn that the combination must be 

 binary ? Why is it not as probable, that water is formed of Objections, 

 two atoms of oxigen and one of hidrogen, of two atoms of 



hidrogen 



