REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 103 



was discovered, which seemed likely to cut off further mining 

 operations at that point. Careful inspection, however, showed 

 that both above and below this pocket of clay, were solid beds of 

 gvpsum. Further investigation showed that, at several points 

 along the walls of the tunnel, smaller pockets ranging in size from 

 a few inches up to three or four feet in diameter had been en- 

 countered. The shape of these pockets was much like an inverted 

 hornet's nest or like a large jug with a small opening at the top, 

 and through the opening the water had found its way to the 

 gypsum, bringing with it clay, which replaced the gypsum as it 

 was dissolved by the water. In all cases the clay is found to 

 follow^ the same lines of stratification as the gypsum; and at first 

 it was the authors opinion that the clay was residual, being left 

 after calcium sulfate had been dissolved. In view of some of 

 the larger pockets however and the nearness of the gypsum 

 deposits at this point to the surface and the broken character 

 of the overlying rock, it seemed certain that these pockets were 

 caused by dissolving the gypsum deposits and replacing them 

 with clay. Strength is added to this supposition by the fact that 

 the limestone underlying the gypsum at this point is unbroken 

 and has a slight dip to the south. The gypsum beds themselves 

 are unbroken, but pockets are found throughout the deposit. The 

 overlying strata, however, are much distorted and broken; but, 

 in view of the lower strata having been subjected to no distortion, 

 no other explanation is left for the broken character of the strata 

 overlying the gypsum than a solution of the gypsum taking away 

 the support from the overlying strata, which naturally would 

 cause the strata to be broken by their own weight. Similar con- 

 ditions have been noticed in quarries and mines throughout the 

 State, and one case has been mentioned by Prof. S. G. Williams in 

 the article which is quoted a little later. 



The distribution of glacial debris in western New York sheds 

 much light not only on the time of the formation of this valley, 

 but on the manner and time of its filling. In the Finger Lake 

 region there is a moraine at the head of each lake, which appar- 

 ently corresponds with the one south of Dansville and Warsaw, 



