562 Professor J. W. .Spencer — Eepit/ to 3Ir. RucUes'on — 



valley, such as is known to have frequently occurred. As an 

 illustration of such obstruction, the ancient Laurentian valley 

 between Georgian Bay (eastern portion of Lake Huron) and Lake 

 Ontario is entirely obliterated, not mei-ely by being filled with drift, 

 but also by high transverse ridges. These Pleistocene accumulations 

 have a depth of 500 to 1,000 feet. Yet the portions of this ancient 

 valley, beyond both sides of the drift filling, are still open channels 

 beneath the waters of the lakes. Again, the differential elevation 

 may in part have raised the barrier across the Norwegian channel. 

 Such a result has been the case in mostly closing the outlet of the 

 basin of Lake Ontario, which is 738 feet deep ; this differential 

 elevation being recorded in the tilting of the beaches adjacent to the 

 lake, but now raised far above it. As the development of this sub- 

 merged channel is a feature very much greater than its partial 

 obstruction, the hypothesis of its subaerial origin has in no wise been 

 overthrown by Mr. Hudleston's superficially - formed conclusion, 

 touched with sarcasm : a conclusion based upon one feature, namely, 

 obstruction, which is much easier of explanation than the occurrence 

 of the submerged Norwegian valley itself, if it were not of subaerial 

 origin. Accordingly, the grand old valley is not yet placed without 

 the pale of the laws of uniformity, which prevail in both subaerial 

 and submarine valleys. 



My conception of the proper treatment of the ' irregularities ' in 

 the continental margin, beneath the waters of the Bay of Biscay, 

 differs greatly from that of Mr. Hudleston. For instance, at a point 

 100 miles south-east of La Chapelle bank, his statement is : — "For 

 at one spot 600 fathoms is marked just outside the 100-fathom line ; 

 while at another, further out to sea, a distance of about seven miles, 

 separate soundings of 880 fathoms and 2,100 fathoms respectively, 

 thus giving a slope of 1 in 5, or 11°. In the latter case, the 

 irregularity is not connected with the edge of the 100-fathom plat- 

 form, but may be said to belong to abyssal depths." His explanation 

 bears only upon the question of the irregularity of the slopes, and 

 does not convey to me any impi'ession that he was making any study 

 of the cirque-like indentation. I should describe the phenomenon 

 as shown upon his own map as follows : — There is a sounding of 

 3,600 feet (600 fathoms), located a few miles within the line con- 

 necting the 600-foot depths on either side, suggesting a cirque in the 

 great continental slope. The trend of this slope on the eastern side 

 of the cirque (or, more correctly speaking, amphitheatre) appears to 

 turn so as to form an embayment due south of the 3,600-foot point, 

 reaching to a depth of 6,420 feet, with a promontory to the east of 

 it rising 860 feet above its floor at this point ; thus showing a great 

 amphitheatre - like valley continuing outward from the 600 -foot 

 platform. Beyond this point the 12,000-foot contour also shows 

 a marked indentation, corresponding to a continuation of this vallej^ 

 noted at depths of 3,600 feet and 6,420 feet, although Mr. Hudleston 

 forms a contrary conclusion. At the head of the amphitheatre, there 

 appears to be a precipitous declivity of about 3,000 feet, but from 

 the foot of this declivity the mean gradient of the valley is about 



