120 CRE SMV ABEL ED Rees 
in spite of its high percentage in the feldspar, while soda, present in 
normal quantity, is conspicuously low in relative solubility. 
The wide divergences from mean relative solubilities shown by 
this experiment are to be accounted for on two grounds. In the 
first place, the conditions of the laboratory only roughly repro- 
duced those of nature; while, in the second place, the feldspar 
varies rather widely from the mean composition of the rocks. 
The former fact may account for the relatively high solubility of 
potash, in spite of its large amount in the feldspar, and the low 
figure for soda, while the latter is doubtless responsible for the high 
figures for lime and magnesia. 
It would be interesting to see what results would be yielded 
by similar experiments upon rocks representing the average surface, 
crystalline areas, etc:, and the writer hopes that such experiments 
may be carried out in future. Meanwhile, the foregoing figures 
are presented not because they are regarded as important in them- 
selves but rather as suggesting a promising line of investigation. 
June, 1912 
