DAVIS : GLACIAL EROSION. 977 
weathered to variable depths in preglacial time. The ice action 
sufficed- to rasp away the greater part of the weathered mate ia 
and to grind down somewhat the underlying rock, often giving the 
knobs a rounded profile; but it did not nearly suffice to reduce the 
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Iig. 2 . Glaciated knobs on the Central Plateau of France. 
» 
SS “ 1" T" Tl » «* *>«•» ~~ lie re to h„. 
‘"™ lop ‘ *- 
"htiero'f r , ex “ nple of * his kincl seems t0 occur where the huge 
fh‘e m 7 6 eSCaplng fr0m itS wel1 enclosed channel within 
the mountains, once spread forward in a great fan of ice over the 
oot-h.1 s at the northern border of the lips and crept out upon 
fronfanT P “' The gla " Ce that 1 ]lad at this district 
om passing ram gave me the impression that its ruggedness was 
much greater than usually obtains along the mountain" flanks; as if 
he rolling hills of preglacial time had been scoured to an increas- 
° toughness by an overwhelming ice-flood that would, if a longer 
time of action had been permitted to it, have worn down all the 
inequalities to a smooth, maturely graded floor. 
7Ae Valley of the Ticino. — My first entrance into the Alps last 
year was from the south by the valley of the Ticino. Thirty-one 
sides 7 °-! 1 had f ° ll0, ' red the same ™lley and admired its' bold 
not Tt nUmerous waterfalls; but at that time nothing was 
oticed that seemed inappropriate to the general idea of the erosion 
