ESKERS IN THE VICINITY OF ROCHESTER, NEW YORK. 211 



About 1,000 feet southeast of this portion of the esker it is again 

 resumed, sloping upward from the plain until a height of 50 feet is 

 attained. Here occurs a large gravel pit, the whole end of the esker 

 being cut away, affording a fine exposure of the internal structure. 

 From here the ridge continues southeastward for 1/3 of a mile with 

 a crest showing frequent knolls and saddles and with a width of 15 

 or 20 feet. The base of the esker here is 100 to 200 feet in width, 

 this width together with the narrow crest and lofty height give steep 

 slopes that become gentler where the knolls occur along the crest 

 line. Sand seems to be common in the saddles, gravel comprises the 

 knolls along this crest line. It is in this segment that the highest 

 knoll occurs, its top rising 80 feet above the surrounding country. 

 Twenty-five rods beyond this knoll the ridge curves abruptly west- 

 ward. Its course may be traced as far as the Erie Canal 1,000 feet 

 or more to the west, however, this portion of the course has been 

 almost entirely cut away for its gravel. This excavation affords the 

 finest exposure of the internal structure and materials of an esker 

 that is to be found in Western New York. Originally this portion 

 of the ridge was of insignificant development, being but about 15 feet 

 high and 25 to 30 feet wide at the base. 



Beyond the canal the continuation of the esker has not been 

 found if it exists. It is possible that it is buried beneath the well- 

 defined kames that are excellently developed here. However, the 

 topography has been much altered due to extensive excavations for 

 the kame sands. 



The internal structure of the esker is well displayed by the 

 numerous gravel excavations already mentioned. The gravel pit at 

 the north end of the southern segment presents the structure in a 

 most satisfactory way. It exhibits the rude anticlinal structure so 

 common in eskers. The stratification is indistinct. The materials vary 

 greatly in size, Medina sandstone making up the larger proportioti 

 of both the fine and the coarser materials. Perhaps 90 per cent, of 

 the mass is of local origin. Boulders 1 foot in diameter occur dis- 

 tributed through the gravels ; boulders larger than this are rare. 

 All of the materials are well rounded by water action. 



At the bottom of the pit the gravel is of the finest character of 

 the whole esker. ]Much of it is but Httle coarser than coarse sand. 



