440 Rev. W. Whewell on the Employment 



atom of silica, A of alumina, C of lime, q of water. Then> 

 15 S + 4 A + C-f 6 (7 will represent a body which contains 15 

 atoms of silica, 4 of alumina, 1 of lime, and 6 of water. If 12 

 atoms of the silica go with the alumina, and 3 with the lime, 

 the symbol may stand thus : (12 S + 4 A) + (3 S + C) + 6 q ; 

 or, what is the same thing, 4 (3 S + A) + (3 S + C) + 6 q ; 

 in which form it is clearly seen that we have 3 atoms of S with 

 1 of A, also 3 of S with 1 of C, and that 4 of the former 

 parcels are combined with 1 of the latter. The same analysis 

 would also give other results, as 4 (2 S + A) + (7 S + C) + 6 7, 

 which is less simple, and so less probable than the former, as 

 the representation of the chemical constitution of the body. 



The expression 15 S + 4 A -f C +6(7, the immediate result 

 of the analysis, may thus be put in various forms ; and these 

 forms are all identical, in virtue of the common rules of 

 algebra or arithmetic. I can hardly conceive how any per- 

 son, at all acquainted with mathematical symbols, can adopt 

 any other mode of notation than this, inasmuch as no other 

 can assist us in reasoning on the constitution of chemical com- 

 pounds. Mr. Herschei long ago employed this mode of 

 notation for such a purpose. In his paper on the hyposul- 

 phurous acid (Edinb. Phil. Journ., 1819), he describes the 

 decomposition of oxynitrate of silver by hyposulphite of lime. 

 L represents lime ; S, sulphur ; .9, silver ; N, nitric acid ; O, 

 oxygen. He says, 6 we have, for the atoms present, before 

 the decomposition, 



which afterwards groupe themselves thus : 



that is, one atom nitrate of lime, one of sulphuret of silver, and 

 one of free sulphuric acid.' In the same manner, in the de- 

 composition of carbonate of oxide of copper by sulphurous 

 acid, c denoting copper, he obtains, 



2(c+0) +2(8 + 20) 



= {(2c+0) + (S + 20)} + (S + 30); 



* that is, two atoms of sulphurous acid disengage the carbonic 



acid from two of the carbonate, producing one atom of sul- 



