on the principal Geysirs of Icelajid. iOS 



M. Damour kindly undertook the analysis of the residue 

 which this water leaves on evaporation, and 1 here transcribe 

 only the results which he has given in a separate notice. A 

 litre of this water, evaporated at 65° centigrade, gives a resi- 

 due weio-hing 1-3900 gr., and effervescing with acids. Heated 

 to 300°,*the weight of this residue was reduced to 1-1830; 

 and at a cherry- red heat the residue agglutinates, and now 

 amounts to only 1'0540. 



The same quantity of water contains,— 



Chloride of sodium 0-2638 



Sulphate of magnesia .... 0-0091 



Sulphate of potass 0-0180 



Sulphate of soda 0-1343 



Soda 0-1227 



Silica 0-5190 



Carbonic acid 0-1520 



Sulphur 0-0036 



1-2225 



The quantities of oxygen of the silica and the bases are in 

 the following relation : — 



ai- Oxygen. Relations. 



Silica . . 0^-5190 0-2696 3 



Soda . . 0-3427 0-0876 \ Q.^^Qg2 1 



Potass . . 0-0097 0-001 6 J 



On subtracting from the weight of the alkalies the quan- 

 tity necessary to saturate the chlorine and the sulphuric acid, 

 there remains, — 



(rr. Oxygen. Relations. 



Silica . . . 0-5190 0-2696 9 



Soda. . . . 0-1227 0-0314 . 1 



In several analyses, M. Damour found that the relation 

 3 : 1 between the oxygen of the silica and that of the bases 

 was constant, and he concluded therefrom that the silica is 

 probably dissolved first in the water of the Geysir, in the 

 state of alkaline silicates, NaO, SiO^, SNaO, 2SiO'', which 

 can be produced artificially, and which are very soluble m 

 water; then, by the action of the sulphurous and hydro- 

 chloric vapours, sulphates and chlorides are formed: the 

 quantity of alkali combined with the silica undergoes a suc- 

 cessive reduction, and the primitive relation of 3 : 1 becomes 

 9:1. In thi.s state of saturation, a portion of the silica ceases 

 to be soluble, and is deposited, without doubt, in a quantity 

 corresponding to the amount of alkali saturated every tlay by 

 the action of the vapour springs, and consequejitly of the 



