I'iiii^cr Lake A'ci^ioii of Central A'. )'. — J arr. 287 
Presence oi' ax Isi.axo in Lake Cayl'(;a : Risin<:j al)()ve 
tliv surface of lake Cayiio-a at L'liion Spritijji's is an island of 
linu'slonc rcick. llow this coukl have been preserved whik" the 
valk'v was heinin" so markedly (!ee])ened by ice erosion has 
always lieen dif'hcull for me to understand, even when ice 
erosion seemed the only explanation of the valley depth. It 
may properl\- be arrayed with the other evidences opposing the 
ice erosion theory. 
Direction of Ice Motion : To accomplish the vast amount 
of work postulated by the glacial erosion theory, the ice must 
have worked under exceptionally favorable conditions, and for 
a long time. As a matter of fact the Cayuga and Seneca val- 
leys lie transverse to the direction in which the ice moved* at 
all times excepting when the ice sheet was so thin as to be 
transformed at its margin to lobes guided in movement bv the 
larger valleys. The distribution of moraines in the Finger 
Lake valleys proves that during its closing stage the ice at- 
tained this condition. The striae which were made during this 
period extend in the direction of the valleys and were earlier 
interpreted to represent the general ice movement as well. 
Whatever marked valley-deepening the glacier accomplished 
in these valleys must have been done in those periods of ice 
advance or retreat when the valleys were occupied bv lobes. 
That the lobes remained in these valleys for some time, dur- 
ing the waning stages of the last ice advance, is proved bv the 
marked development of moraines. It is also proved by the fact 
that, while north of the moraines of these valley lobes the 
glacier in most places scoured away the clays of residual 
decay, south of the valley moraines residual clays are exceed- 
ingly abundant, appearing in scores of places.* 
The facts stated in the last two paragraphs, while not 
directly opposed to the ice erosion theory, tend to weaken it. 
For they show ( i ) that the glacier accomplished little work 
of erosion during its advance over the region which lies south 
of the massive moraines that occupy the vallevs at the heads 
of the Finger lakes, having been incompetent to remove the 
rock below the zone of decay; (2) that during this time, and 
• The evidence of this, as well as the nature of the moraines of this region, 
will be presented in the discnssion of the Pleistocene jreology of the Watkios 
Glen folio, now in preparation. 
