1865.] CHEMISTRY OF NATURAL WATERS. 181 



from Byron, little more than a solution of sulphuric acid. The 

 observations of Eaton at Byron, and my own at Tuscarora, show 

 that half-decayed trees are still standing on the soil which is now 

 so impregnated with acid waters as to be unfit to support vegeta- 

 tion. Reasoning from the changes in composition, it may be sup- 

 posed that these waters were at first neutral, the whole of the 

 acid being saturated by the calcareous rocks through which they 

 must rise. It was from this consideration that I was formerly 

 led to ascribe to the action of these waters the formation of some 

 of the masses of gypsum which appear along the outcrop of 

 the Onondaga salt-group (Silliman's Journal [2], vii, 175). That 

 waters like those just mentioned must give rise to sulphate 

 of lime by their action on calcareous rocks is evident ; and some of 

 the deposits of gypsum in this region, as described by good 

 observers, would appear to be thus formed. So far however as 

 my personal observations of the gypsums of western Canada have 

 extended, they appear to be in all cases cotemporaneous with the 

 shales and dolomites with which they are interstratified, and to 

 have no connection with the sulphuric-acid springs which are so 

 common throughout that region. (Silliman's Journal [2], xxviii? 

 365, and Geology of Canada, 352.) 



§ 50. We have included in a sixth class the various neutral 

 saline waters in which sulphates predominate, sometimes to the 

 exclusion of chlorids. The bases of these waters are soda, 

 potash, lime, and magnesia; which are usually found together, 

 though in varying proportions. For the better understanding of 

 the relations of these sulphated waters, it may be well to recapitulate 

 what has been said about their origin ; and to consider them, from 

 this point of view, under two heads. 



First, those formed from the solution of neutral sulphates pre- 

 viously existing in a solid form in the earth. Strata enclosing na- 

 tural deposits of sulphates of soda and magnesia, sometimes with 

 sulphate of potash, (§ 17, § 19,) afford the most obvious source 

 of these waters. The frequent occurrence of gypsum however 

 points to this salt as a more abundant source of sulphated waters. 

 Solutions of gypsum may in some case exchange their lime for the 

 soda of insoluble silicates, or this salt may be decomposed by solu- 

 tions of carbonate of soda (§ 7, § 19). The decomposition of the 

 sulphate of lime by hydrous carbonate of magnesia, as explained in 

 § 21, is doubtless in many cases the source of sulphate of mag- 

 nesia, which is more frequently than sulphate of soda a predomi- 



