— 
349 
on which day there was least moisture in the air, is the mean 
of the whole three observations. 
Sir Robert Kane brought under the notice of the Aca- 
demy the results of the analysis of the waters of the streams 
which descend from the side of the Dublin mountains, such 
as the Three Rock Mountain, with a view to illustrate the 
process of decomposition of the granite masses of those rocks, 
and the conversion of the felspathic elements into claysadapted 
for ceramic manufactures. A great number of springs and 
wells along the line of hills from Glencullen to Dundrum had 
been examined, and with similar results; but Sir Robert Kane 
specially detailed the quantitative analyses of two waters from 
Ticknock, above Rathfarnham, on the flank of the Three Rock 
Mountain. 
The first of these specimens of water was taken from a 
rapidly running stream, and it was found that it contained a 
considerable quantity of soluble silica, combined with alkalies, 
there being both potash and soda present. This stream passed 
over a considerable tract of decomposing granite: 148,000 
grains of this water left a residue on evaporation of 12:5 grains. 
This residue was found to contain the ordinary constituents of 
surface water, but in addition, alkalies and silicates amount- 
ing to— 
Sites, ¢eMiek ile Sits ,062 
: tidy 5s ree nls hay cee 245100. 
Soda, 0% «meet aust hy, weaved 
The presence of alkaline silicates in such quantity in this 
water induced Sir Robert Kane to have a still more detailed 
analysis made of the water contained in a cavern excavated in 
one of the quarries made for obtaining what is called freestone, 
that is, the coarse powder of decomposed granite used in Dub- 
lin for scrubbing floors. This water was stagnant, and was de- 
rived from drainage through the adjoming masses of decompos- 
