244 NATURAL SCIENCE. Oct.. 



There is a uniform minimum slope which they constantly seek to 

 establish and maintain. Any movement of the land leaves its record 

 in a change in the intensity of the action of the stream, whether it 

 be cutting or depositing ; and in non-glaciated regions streams are 

 now systematically examined by geologists for the purpose of ascer- 

 taining whether the country traversed by them has been uplifted or 

 depressed, or has maintained a fairly constant altitude. Evidence 

 of this kind, however, is not always available, and it is necessary to 

 turn to other features. For instance, there are some regions in which 

 the shores of ancient lakes can be traced for many miles — in the 

 centre of North America sometimes for hundreds of miles. These 

 old beaches must, of course, have been originally horizontal, and if, 

 therefore, any one of them appears now to be displaced, variously 

 inclined, and at somewhat different levels in different parts, there is 

 clear evidence of movements of the crust since the lake dwindled or 

 disappeared. Such evidence of earth-movements has been known 

 for some years in North America on either side of the Lake Superior 

 basin,' and Professor A. C. Lawson's investigation of the old beaches 

 to the north of the present Lake Superior was undertaken with the 

 object of ascertaining how far the effect of movements could be 

 traced in that region. A beautifully illustrated detailed report leads 

 to the conclusion that there once existed an enormous " Lake 

 Warren " (to use Professor Spencer's term) probably at least twice 

 as great as the combined areas of the present lakes Superior, 

 Michigan, and Huron, or about 150,000 square miles. In some places 

 as many as nineteen distinct beach-lines can be traced along the 

 northern shore of Lake Superior, and Professor Lawson believes 

 there is evidence of at least thirty-two definite stages in the 

 recession of the lake. It seems probable that the lowering of the 

 water was gradual, though perhaps varying in amount at different 

 times ; and it is hardly possible to believe that the existence of ice 

 barriers had any connection with the phenomena. It is likely, 

 therefore, that the local warping of the earth's crust, in some region 

 far removed from Lake Superior, is accountable for the lowering of 

 the land barrier which held back the waters of " Lake Warren." 

 The outlet may even have been at different places at different times 

 in consequence of the unequal continental warping of which there 

 is evidence elsewhere. Professor Lawson enumerates the possible 

 situation of some of these outlets, and makes many suggestions 

 that will be of much service to future observers, both in this 

 and other ree^ions. 



The Peeding of Fishes. 



It is well-known that the sense of smell in fishes is very keen, 

 and that all use it more or less in feeding, whether or not sight aids 



1 See "Great Lakes," by Clement Reid, Nat. Sci., vol. i., p. 117. 



