212 ROCHESTER ACADEMY OF SCIENCE. 



Here the stratification is scarcely discernible, being best brought out 

 by layers of small well rounded pebbles occurring in the fine gravel 

 deposit. The stratification is most irregular, now dipping one way, 

 again in another direction. At each side of the pit the dip is out- 

 ward at an angle of about 10 degrees. The gravel here extends 

 considerably below the general surface on either side of the esker. 



At about 10 feet above the floor of the pit there is a peculiar 

 development decidedly unusual in eskers so far observed. This con- 

 sists of a layer of almost uniform thickness, of about 3 feet, which 

 extends across the whole esker in a horizontal plane. It is composed 

 almost entirely of small pebbles of uniform size, with few larger 

 stones or boulders. The whole mass is so firmly cemented that it is 

 almost impossible to break it with a sledge. It is necessary to dis- 

 lodge it with dynamite to get at the gravel underneath. Great masses 

 of this layer have been left strewn about the floor of the pit and in 

 the adjoining field. This cemented layer lies in the plane of the 

 latest and highest Iroquois waters. It is suggested that the calcareous 

 cement was carried down by leaching atmospheric waters and was 

 deposited when the zone of the standing waters was reached. The 

 layer is the most striking feature of the excavation and immediately 

 attracts attention. 



At the southeast end of this excavation, of which this peculiar 

 layer forms the floor, is found much the same features. Here the 

 stratification is indistinct and appears frequently to be entirely want- 

 ing. The materials are unassorted, the coarser being mingled in 

 profusion with the finer. This is especially true near the extreme 

 top of the ridge. Here coarse boulders, 8 to 10 inches in diameter, 

 occur in profusion. 



On either flank of the ridge, as revealed in this excavation, a 

 layer of fine sand occurs, 4 to 8 feet in thickness, extending from a 

 line 15 feet from the crest half way down the slopes. This probably 

 represents wind blown accumulations subsequent to the formation 

 of the esker. 



Southeast of this extensive excavation along the railway track 

 there is another gravel pit which afifords a good quality of gravel of 

 uniform size. The exposure exhibits distinct stratification, the strata 

 dipping outward. 



