Geological Reports on the State of New York. 39 



of limestone dip upon every side of the mass of gypsum, and as this mass 

 thins off at its edges, the strata of limestone meet those below and assume 

 their original, nearly horizontal position. From such appearances we 

 cannot doubt but the gypsum has been formed since the surrounding rock 

 became indurated; and that the production of these masses has disturbed 

 the overlying strata. The decomposition of large quantities of iron py- 

 rites might, perhaps, explain the formation of gypsum, by a decomposition 

 of the limestone, but there is very little pyrites now remaining in the rock. 

 The masses of gypsum are sometimes stained on their edge with iron, and 

 bog ore is of frequent occurrence in the neighborhood. Hydro-sulphur- 

 etted springs are common, and the water of some wells is of similar char- 

 acter. The water of some of these springs corrodes iron rapidly. In the 

 town of Byron, Genesee county, there is a spring arising from this forma- 

 tion, containing free sulphuric acid. 



" Immediately surrounding each mass of gypsum we find layers of 

 loamy clay, called ashes by the workmen. This ashes contains dissemi- 

 nated particles, and sometimes scarcely aggregated, friable masses of gyp- 

 sum. We have in this " ashes" precisely what would remain of the argil- 

 laceous limestone, should we abstract the calcareous matter by sulphuric 

 acid, or any other process. 



" It is said by the inhabitants, that the small elevations indicating the 

 presence of gypsum are not observed till after the country has been cleared 

 of its forests, or in places where there have never been trees growing. 

 These changes in the contour of the surface are observable from one year 

 to another. In some places a mass of gypsum has formed under a build- 

 ing, altering the level of its foundation and disturbing its equilibrium. 

 Points on the surface which are now but slight elevations, will in a few 

 years become more elevated." 



Boulders and diluvial scractches, 6^c. — Gravel, sand, pebbles, 

 and boulders, are strewed more or less over the country, 



" These boulders consist of the various granites and gneiss, together 

 with those of the sandstone from below, and of the limestone from above. 

 Besides this unequivocal evidence we have other, and if possible, more 

 positive proof, in the furrowed and polished surface of the limestone, which 

 is seen wherever the rock is exposed, from the Genesee to the Niagara 

 river. The surface of this rock bears palpable evidence of the wearing 

 action produced by running water, carrying with it heavy materials of 

 sufficient hardness to wear away, and in some instances, actually to polish 

 the surface of the rock over which it passed. Where the rock is exposed 

 we find the surface has been worn, in some instances, till it is perfectly 

 smooth, and in others the original inequalities are but partially obliterated. 

 We often observe that the abrupt offsets from one thin stratum to another, 

 have been worn down to a gradual slope. In some places slight scratches 



