402 PROCEEDINGS OF COLUMBUS MEETING. 



at 1,190, 1,170 and L, 130 feet. The terraces continue on the southern side of the 



divide, and at a point ten miles distant were noted at 1,095, 970, 940, 888 and 830 

 feel, with the floor of the valley 770 feel above tide. With the differential warping 

 considered, the identity of the upper terraces is unquestionable. The summit of 

 the divide is not covered with a gravel deposit ; but a short distance southward 

 gravel deposits were seen, though their altitude was not measured. 



Let us now ask, What harrier retained the volume of water 325 feet above its floor 

 in a valley one to two miles wide, with the opening country descending in the next 

 ten miles another .'!2.~> feet? Here we have the action of water in a great open 

 embayment leaving records at an elevation of 650 feet without any harrier on the 

 south, unless these waters were retained against the now high level hanks, owing 

 to a submergence of the region down to sea-level, as it can scarcely he supposed that 

 a glacial dam could have occurred upon the southern side of a lake. The absence 

 of the terrace deposits on the divide is easily explained by tin' action of tidal cur- 

 rents and need not be considered the proof of a glacial river flowing over the water- 

 shed into a great embayment which could not have retained the volume of water 

 passing over the divide at hundreds of feet above the bottom of the valley without 

 an obstruction or submergence to the south. The lower terraces are confined to 

 the valleys and are not specially considered. Here, then, we And a col connected 

 with terraces on the northern side, such as are often quoted as proof of glacial 

 dams, but the terraces on the southern side disprove the efficiency of ice dams to 

 account for this class of high level terraces. 



Professor C. W. Hall was called to the chair, and discussion on the 

 matter of the three preceding papers occurred, participated in by W J 

 McGee, G. K. Gilbert, -J. E. Wolff, 1. C. Russell, G. F. Wright and J. W. 

 Spencer. Mr. Gilbert spoke as follows on Dr. Spencer's papers: 



The Iroquois shore-line or group of shoredines has been traced about three- 

 fourths of the Ontario basin. At the west it lies 100 feet above the modern lake, 

 and it rises toward the northeast. On the northeastern side it has not been traced 

 and in that direction there is no land high enough to receive it. As I interpret 

 the phenomena, the Iroquois water was retained on that side by a glacier occupy- 

 ing the Saint Lawrence valley, and its surface level was determined by the altitude 

 of a divide at Koine over which the surplus water found outlet, flowing eastward 

 down the Mohawk valley. It is Dr. Spencer's view that the Iroquois water stood 

 at the level of the sea, the land being depressed at that time. Tracing the shore- 

 line about the southern and eastern sides of the basin, I was aide to map it to the 

 vicinity of Watertown, where it turns northeastward, lint a few miles beyond I 

 found the record faint and finally untraceable. At the point where continuous 

 observation ceased to be practicable the surface of the country is not well suited 

 to the preservation of a sboi-e record. It consists of a broad plain of sand with 

 so little admixture of finer material that it is the prey of the wind and is re- 

 sculptured into dunes. It seemed possible that beach ridges might have been 

 formed upon this sand plain and afterward obliterated. A detour was accord- 

 ingly made and the country beyond the sand plain was examined through a 

 range of altitude including that of the Iroquois beach, in the hope of picking 

 up it< record once more and following it eastward; but it was not discovered, 

 although the ground appeared favorable for the reception and preservation of 



