292 Tertiary. 



Grooves or striae are found upon the surface of all the rocks beneath 

 the drift in the fourth district, which are of sufficient hardness to re- 

 ceive and retain such impressions. From the Medina sandstone, at the 

 level of lake Ontario, to the summit of the Carboniferous conglomer- 

 ate, in the southern i)art of the State, some of the strata in every group 

 bear upon their surface these markings of former abrasion, and 

 evidence of moving force. The direction of these striae vary but few 

 degrees from N. 35° E. and S. 35° W. in their general course. Short 

 and shallow striae are abundant, which vary ten and fifteen degrees 

 from this direction, but these have no continuous course, and apparent- 

 ly fall into the main direction after a few feet. These markings range 

 from the slightest possible scratch, to grooves of half an inch in width 

 and one fourth of an inch in depth. The grooves seem to have been 

 made b}' a hard substance, moved with great force and under great 

 pressure, for fragments are found broken out as the grooves approach a 

 fissure in the strata, as if crushed out by some heavy body, and some- 

 times the grooves are observed following, somewhat obliquely, the 

 fractured slope. The outcropping edges of strata, previousl}- polished 

 and grooved, are often found overturned, upon the rock, in place. 



At Rochester, the surface of the limestone is finely striated, and al- 

 most perfectly polished by the abrading force. The material here rest- 

 ing upon the rock is fine sandy loam; in another locality a mile farther 

 south, it is covered by coarse limestone gravel and sandstone pebbles, 

 with bowlders of granite. The striae here are N.N.E. and S.S.W. At 

 Black Rock, the surface of the Corniferous limestone shows that the 

 nodules of horustone interrupted the progress of the striae and stand 

 above the surrounding polished surface. The direction here is N. 15° 

 E. and S. 35° W. At the clift'ofLake Erie in Portland, Chautauqua 

 county, the rocky strata below have been uplifted, broken and con- 

 torted; the fragments intermingled with clay and gravel, and the same 

 pressed beneath the strata, which otherwise appear to be in place. 



The terrace at Lewiston is formed by the upper part of the Medina 

 sandstone, the Clinton Group and the Niagara shale, capped by al^out 

 twenty feet of Niagara limestone. The top of this terrace is 350 feet 

 above Lake Ontario, and more than 200 feet above the plain about 

 Lewiston. The Niagara shale is carried awa}' so as to leave tlie lime- 

 stone of the Clinton Group lorming a projecting shelf about 100 feet 

 below the top of the terrace. The surface of this projecting shelf is 

 deeply grooved and striated, the grooves having a general southern 

 tendenc}^ but more irregular than where the}' are seen upon the lime- 



