IO 
BULLETIN 82. 
tended to assert that this mineral is the only one on which the 
water, carbonic acid, and whatever other agencies co-operate with 
them act, bnt it is the principal one; and this is true to such an ex¬ 
tent that we may neglect all others. The prevailing rock within 
the drainage area is either granite, gneiss or mica schist. There 
are a few ernptives within this area, and locally a little hornblende- 
schist occurs; bnt these form no large areas, so we confine ourselves 
to the consideration of the felspar of the granite, which is an 
orthoclase. This statement does not exclude the occurrence of 
other varieties, bnt they are altogether subordinate. The preced¬ 
ing facts constituted one reason why I chose a typical orthoclase 
for experimentation. A second reason was the observation that onr 
soil consists largely of grains of this mineral. The results of ex¬ 
periments with this mineral then give 11s a measure whereby to 
judge to what extent the Pondre water obtains its mineral matter 
from this source; and, secondly, a clue as to what is going on in the 
soil, which, however, is only of incidental interest at this time. 
§ 22. A portion of felspar, orthoclase, was ground very fine, 
passing through a 1 oo-mesh sieve, and treated for 22 days with 
water containing carbon dioxid in solution. At the expiration of 
this time air was caused to pass through it whereby any ferrous 
salts would be oxidized and the ferric hydrate precipitated. By do¬ 
ing this we imitate the action which we see taking place in the 
river waters, especially when derived from springs in whose waters 
iron may be held in the form of ferrous salts. We found in this 
case that we obtained a copious precipitate of the hydrated ferric 
oxid. The filtered water was evaporated in platinum dishes to 
avoid obtaining any silica or potash, as might have been the case 
had we used a porcelain or copper dish to evaporate in. The 
amount of total solids obtained corresponded to 1.68 grains to the 
imperial gallon. I will here observe that the results of all the ex¬ 
periments that I made indicate that the amount dissolved is pro¬ 
portional to the time the water is in contact with the felspar, at 
least for such times as my experiments continued, other conditions 
being the same. The residue obtained had the following com¬ 
position:— 
