1876.] 277 [Niles. 



to the direction of its action, as the force operating upon the gneiss 

 at Monson, Mass., is certainly highly interesting and instructive. 



Before considering the geological significance and importance of 

 these evidences, I desire to present the results of some observations 

 made at another locality, which extend the interest attached to these. 



OBSERVATIONS AT LEMONT, ILLINOIS. 



At Lemont, Illinois, about twenty-six miles south-west of Chicago, 

 there are a large number of quarries in the Niagara limestone of that 

 region. When I visited this locality in the summer of 1864, I was 

 informed that a curious unconformability in the position of the upper 

 and lower parts of certain pot-holes in the rock was occasionally ob- 

 served. These statements have since been recorded by Dr. Henry 

 M. Bannister, in his report upon the Geology of Cook Co., contained 

 in the third volume of the Reports of the Geological Survey of 

 Illinois. So far as I know, this is the only published notice of these 

 appearances, therefore I quote' Dr. Bannister's account in full. 



" It is stated that the pot-holes, which have been already mentioned 

 as occurring in the water-worn surfaces of the upper layers in the 

 Athens 1 quarries, when of sufficient depth to penetrate one layer and 

 enter another, are occasionally found to be dislocated — that is, one 

 layer has slipped upon the other, so that the upper and lower portions 

 of the pot-hole are, in some cases, entirely separated from each 

 other. I was not myself so fortunate as to observe a case of this 

 kind, but the fact of their occurrence seems to be well attested. It 

 would appear to indicate a slight disturbance of the strata, at a com- 

 paratively very recent period, subsequent even to the Terrace epoch, 

 during which these holes were probably formed. The dip is hardly 

 perceptible, not more than one or two degrees to the south-east, in 

 Singer and Talcott's quarries, where these appearances have been 

 most observed — the disturbance is, therefore, very slight, and it is 

 quite probable that it was also very gradual." 



On a recent visit to this locality, I found some interesting evi- 

 dences that such a geological action is still in progress. In a quarry, 

 of the Illinois Stone Co., at Lemont, there was, Nov. 27th, 1875, an 

 elevation of a part of the bed forming the floor of the quarry. It 

 was an anticlinal axis of more than eight hundred feet in length, and 

 its trend was nearly east and west. In its most conspicuous part the 



* The stone is known as Athens marble. 



