138 ROCHESTER ACADEMY OF SCIENXE. 



moraine, declines rapidl}- northward from the 380 contour and 

 passes under a thick cover of silts at the Sea Breeze end. In the 

 road cutting there the silts are seen to be much contorted, a phenom- 

 enon noticed also at Summerville and other points along or near 

 the delta edge by Prof. Fairchild, and attributed by him to a spread- 

 ing flow or "creep" of the basal layers of the delta deposit under 

 the increasing superincumbent load, or as the waters withdrew. 



The remarkable triune amphitheater southeast of this ridge, en- 

 compassed by the trolley, will be considered under the erosional 

 history. 



Lake Euunons delta and terraces. We now pass from the de- 

 posits of Lake Iroquois to those of the first conspicuous halt in the 

 lowering of its waters probably identical with that which Fairchild 

 has elsewhere called Lake Emmons, but the nature of which he has 

 more recently doubted. The matter of interpretation need not con- 

 cern us here, if the fact of a recognizable and continuous strand is 

 established; nor is a new name necessary, since in any case the sole 

 communication of the Emmons waters with the sea must have been 

 through the narrow strait at Whitehall, with the flow all in one 

 direction. 



The Emmons delta of the Genesee is at Windsor Beach, with 

 an inshore elevation of below 320 feet (probably about 310 j. A 

 portion of it a])pears in the extreme northwest corner of our map, 

 showing traces of the old distributary channels on its surface. The 

 ''White City" stands on this plain, whereas "Elm Beach" occupies 

 the beach level of Lake Ontario. (These not on map). The Emmons 

 shore is everywhere weak and this delta is further disguised by being 

 built against the lower slopes of the much larger Iroquois delta, from 

 which it was therefore not discriminated at first. But while the 

 Iroquois plain extends northward on the Summerville Boulevard to 

 "Cole Road" (sec xvcst edge of map) with a nearly level surface, 

 it then begins to decline noticeably. This slo])e continues halfway 

 to the next turn in the road, where it ceases and the Emmons plain 

 commences. Faint wave work and notchings are visible just above 

 the inner margin of that plain at about the 320 contour, with some 

 pebbles and gravel ice-rafted along the beach in winter. The shore 

 bears thence nearlv due east, discernible chieflv as a change in 



