126 ROCHESTER ACADEMY OF SCIENCE. 



surfaces of this region held impounded waters whose points of 

 escape lay to south or west or east. Some of these waters were 

 small and local lakes, but others were truly inland seas, greater than 

 the existing Great Lakes their descendants. The broader history of 

 these lakes, so far as it had been unravelled, has been told by Fair- 

 child.' Of the lakes described by him, the earlier ones. Hall, 

 Vanuxem. and \\'arren. involved more or less of the Ui)per Ironde- 

 Cjuoit Valley but probably did not enter the area immediately under 

 discussion because it was still ice-covered. At least the ice reached 

 fnto the upper valley during the existence of the succeeding Lake 

 Dana for there is an ice-margin deposit (esker fan) built in Dana 

 waters at Railroad ]\lills (715 feet A. T.). At some time, however, 

 during or subsequent to" Lake Dana the kame deposits of the Pin- 

 nacle Range just south of Rochester (see Plate III) were being 

 constructed at the margin of the Genesee ice-lobe ; and it is interest- 

 ing to note that their highest summit at 750 feet accords with the 

 rising Dana plane on this parallel. It is possible, therefore, that 

 before its extinction Lake Dana was admitted into the southwest 

 corner of our map-area. 



After Dana came a brief pause at aboiit 540 feet that has left 

 faint marks on the south face of Cobb's Hill and the Pinnacle and 

 on the north end of certain drumlins south of Fairport ; then Lake 

 Dawson at 480 feet, whose more conspicuous effects are described 

 beyond, and next Lake Iroquois at 435 feet, whose work occupies 

 the bulk of this paper. Iroquois was by far the most im])ortant and 

 most enduring of these water bodies. Its outlet was throtigh the 

 ]\Iohawk Valley at Rome, N. Y., and at its zenith it filled the 

 Ontario-Saint Lawrence Valley to the northmost bounds of our 

 State. 



Two stages in the lowering of Lake Iroquois waters have been 

 recently [as of 1909] discerned by the writer'' in northern New 

 York, and since traced and mapped by Fairchild into the Champlain 

 and Hudson Valleys.'' The higher of these had already been noted 

 by me at about 320 feet in the Rochester district ; the other prol^ably 



5. Bulletin 127 X. Y. State Museum: Glacial Waters in Central Xevv York. This 

 work was just going through the press when the present paper was written. 



6. Bulletin 14.'5 X. Y. State Museum, p. 1:59 footnote: and Bull. 14!». ii. Is. 



