120 Gregory — Progress in Interpretation of Land Forms. 



Matthew (1871) 49 reached the same conclusion for the 

 Lower Provinces of Canada. In spite of the increasing 

 clarity of the evidence, the battle for the glacial theory 

 was not yet won. The remaining opponents though few 

 in number were distinguished in attainments. Dawson 

 clung to the outworn doctrine until his death in 1899. 



An interesting feature of the history of glacial theories 

 is the calculation by Maclaren (1842) 50 that the amount 

 of water abstracted from the seas to form the hypo- 

 thetical ice sheet would lower the ocean-level 350 feet — 

 an early form of the glacial control hypothesis (see 

 Daly 51 ). 



Extent of Glacial Drift. 



By the middle of the 19th century, it was recognized 

 that the " drift, " whatever its origin, was' not of world- 

 wide extent. In America its characteristic features were 

 found best developed north of latitude 40 degrees ; in 

 Europe, the Alps, the Scottish Highlands, and Scandi- 

 navia were recognized as type areas. The limits were 

 unassigned, partly because the field had not been sur- 

 veyed, but largely because criteria for the recognition of 

 drift had not been established. The well-known hillocks 

 and ridges of "diluvium" and ''alluvium'' and "drift" 

 of New Jersey and Ohio, and the mounds of the Missouri 

 Cotou elaborately described by Catlin (1840) 52 bore 

 little resemblance to the walls of unsorted rock which 

 stand as moraines bordering Alpine glaciers. The 

 Orange sand of Mississippi was included in the drift by 

 Hilgard (1866), 53 and the gravels at Philadelphia bv 

 Hall (1876). 54 Stevens (1873) 65 # described trains of 

 glacial erratics at Richmond, Virginia, and Wm. B. 

 Rogers (1876) 56 accounts for certain deposits in the Poto- 

 mac, James, and Roanoke rivers by the presence of 

 Pleistocene ice tongues or swollen glacial rivers, and 

 remarks: "It is highly probable that glacial action had 

 much to do with the original accumulation of the rocky 

 debris on the flanks of the Blue Rid^e, and in the Appa- 

 lachian valleys beyond." Kerr (1881) 57 referred the 

 ancient erosion surface of the Piedmont belt in North 

 Carolina to glacial denudation, De la Beche compared 

 the drift of Jamaica with that of New England, and 

 Agassiz interpreted soils of Brazil as glacial. 



