1865.] CHEMISTRY OF NATURAL WATERS. 5 



sodium might acquire a considerable amount of chlorid of calcium ; 

 but it is probable that these reactions, however important they may 

 be in relation to the soil, and to surface-waters with their feeble 

 saline impregnation, have at present but little influence on the 

 composition of the stronger saline waters. It is however not 

 impossible that the action of the ancient sea-waters, holding a 

 large amount of chlorid of calcium, upon the hydrated and half- 

 decomposed feldspars which constituted the clays of the period, may 

 have given rise to those double silicates which formed the lime- 

 soda feldspars so abundant in the Labrador series. 



§ 8. The reactions just described assume an importance in the 

 case of waters impregnated with soluble matters from vegetable de- 

 cay ; and in this event, another and not less important class of phe- 

 nomena intervenes, which are due to the deoxydizing power of the 

 dissolved organic matter. By the action of this upon the insoluble 

 peroxyd of iron set free from the decomposition of ferruginous 

 minerals and disseminated in the sediments, protoxyd of iron is 

 formed, which is soluble both in carbonic acid, and in the excess 

 of the organic (acid) matter. By this means not only are great 

 quantities of iron dissolved, but masses of sediments are sometimes 

 entirely deprived of iron-oxyd, and thus beds of white clay and 

 sand are formed. The waters thus charged with proto-salts of iron 

 absorb oxygen when exposed to the air, and then deposit the 

 metal as hydrated peroxyd, which when the organic matter is in 

 excess, carries down a greater or less proportion of it in combina- 

 tion. Such organic matters are rarely absent from limonite, and 

 in some specimens of ochre amount to as much as fifteen per cent.* 

 The conditions under which hydrous peroxyd of manganese is 

 often found are very similar to those of hydrous peroxyd of iron 

 with which it is so frequently associated ; and there is little doubt 

 that oxyd of manganese may be dissolved by a process like that 

 just pointed out. A portion or manganese has been observed in 

 the soluble matters from decaying peat-moss ; and it seems to be 

 generally present in small quantities with iron in surface-waters. 



§ 9. There is reason to believe that alumina is also, under cer- 

 tain conditions, dissolved by waters holding organic acids. The 

 existence of pigotite, a native compound of alumina with an 

 organic acid, and the occasional association of gibbsite with lim- 

 onite, point to such a reaction. That it is not more abundant in 



* Geology of Canada, p. 512. 



