350 



ing granite : 88,000 grains of this water gave a solid residue 

 of 10-50 grains; containing organic matter, 2*47 grains. 



The complete analysis of this solid material showed it to 

 contain per cent. — 



Organic matter (crenic and apocrenic acids), . 23-30 



Carbonic acid, 7-40 



Muriatic acid, 17-99 



Sulphuric acid, 6*34 



Silica, 3-81 



Lime, 3-03 



Magnesia, 0.85 



Potash, 2-86 



Soda, 30-48 



Loss, . 3-94 



100-00 

 The large quantity of muriatic acid in this water is of course 

 present as chloride of sodium, derived from the vapours carried 

 over to those mountains from the immediately adjoining sea. 

 This 17*99 of muriatic acid takes, therefore, 15-28 of soda to 

 form common salt. The state of combination in which the 

 sulphuric acid may have been in is not so easily assigned; but 

 even if we allocate to it the strongest alkalies, there will still 

 remain a large quantity, about 12-16 per cent, of soda, which 

 must have been combined with the silica, and with the organic 

 acids. 



The characteristic feature of those waters, which may be 

 considered as the types of those flowing down the flanks of 

 the granite hills south of Dublin, is the presence of consider- 

 able quantities of alkaline silicates, principally silicate of soda. 

 This might be expected, as it verifies the mode of decomposi- 

 tion of granitic rocks, and the deposition of china clays, sug- 

 gested by Brogniart and others, but the instances in which the 

 waters of such localities have been accurately examined, and the 

 actual removal therein of the alkalies and silica of the felspa- 



