446 Rev. W. Whewell on the Employment 



and a part soda, such portions of the two alkalis entering as to 

 Ynake up together a proportional ingredient. Thus we may have 

 aK and -J-N ; and the mineral would then be (9) = 8 S -f 

 3A + K + iN + 6q. And4 x (9) = 32S + 12A + 

 (3K 4. N) + 24(/ : in which, instead of 4 K, we have 3 K 

 -f- N ; one atom of potassa being replaced by one atom of 

 soda. In obtaining such formulae from experimental analysis, 

 the number of atoms of the two isomorphous ingredients must 

 be added together, including their fractional parts, before we 

 attempt to compare the atoms of different ingredients. And 

 in the resulting formula, the symbols of the isomorphous in- 

 gredients may be written after each other with commas, thus, 



(9) Chabasite = 8S + 3A-fC, R, N, + 6 q 



= 3 (2 S + A) + (2 S + C, K, N,) + 6 q ; 



in which C, K, N, may be read C, or K, or N. And the 

 composition of different varieties would be 



8S +3A + C -f 



8S + 3A+ 3 



If such a notation as this were adopted, it would be highly 

 desirable that there should be a general understanding among 

 chemists and mineralogists with regard to the letters by which 

 elements are to be designated ; for we should then be able to 

 use the formula without preface, with a great gain of brevity 

 and clearness. The obvious method is to take the initial letter 

 of the word for the symbol of the element, except when there 

 are reasons to the contrary. Thus we have A, alumina ; B, 

 baryta; C, calcia (lime) ; G, glucina; L, lithia; M, magnesia; 

 N, natron, or soda (for S is wanted to express silica) ; K, 

 kali, or potassa; S, silica; Y, yttria ; Z, zirconia ; strontia 

 may be represented by Sr. It may help the memory to observe 

 that K, L, N, three letters near each other in the alphabet, 

 represent the three alkaline earths. P is wanted for phos- 

 phorus ; and K and N are thus used by Berzelius. 



In these cases the earth or oxide of the base only occurs ; 

 the bases themselves, aluminium, barium, &c. ; not entering 



