on and near the Erie Canal. > 41 



milk. I heard several other sour springs mentioned, which 

 I had not time to visit. This is to be expected ; for the same 

 variety ofanalluvion prevails over a considerable extent of 

 territory. The towns of Wheatland and Chili, in Monroe 

 county, and the towns of Bergen and Byron, in Genessee 

 county, have a most excellent soil for the growth of wheat. 

 It seems to consist mostly of disintegrated lias. There are 

 numerous knowls, or hillocks, which contain insulated mas- 

 ses of gypsum, similar to that which is taken from the lias in 

 Manlius, &c. The iron pyrites which pervades the soil 

 throughout these and other adjoining towns, is the same 

 soft granulated variety which is found in the soft pyritiferous 

 slate of Lake Erie, Cayuga Lake, &c. 



Here a question of some importance presents itself. Why 

 is all the sulphuric acid, produced by the decomposition of 

 iron pyrites in some localities, wholly combined with the 

 iron, forming sulphate of iron ; while free acid is left in other 

 localities; and a surplus in others which combines with mag^ 

 nesia, alumine, &.c. ? Is the pyrites a per-sulphuret in the 

 latter case, and a proto-sulphuret in the former ? Or are the 

 iron and sulphur more perfectly combined in the former 

 case ? In support of the latter suggestion, it should be ob- 

 served, that it is almost impossible to produce sulphuretted 

 hydrogen gas with native cubic crystals of iron pyrites ; while 

 we do it with so much facility with the artificial and also 

 with the native granulated variety by the aid of heat. 



Whether or not we can assign the cause, the fact is cer- 

 tain, that by the decomposition of that variety of iron pyrites, 

 whose grains can scarcely be seen without the aid of a lens, 

 sulphuric acid is produced in quantities sufficient for forming 

 alum and epsom salts in numerous localities. It is very pro- 

 bable that carbonate of lime is decomposed by the same 

 agency ; thus furnishing the immense supply of carbonic 

 acid in the Saratoga waters. 



6. Sulphate of Magnesia. 



It is a curious fact that sulphate of magnesia had never 

 been announced as an American mineral until Dr. T. R. 

 Beck and myself published an account of the Coeyman's lo- 

 cality, in Mr. Van Rensselaer's Albany County Survey of 

 1820. Now it would require several pages to enumerate 

 the known localities adjoining the Erie cana! line. The very 

 strong epsom salt spring at Coeymans in Albany county, the 



6 



