88 



SCIENCE. 



[N. S. Vol. XV. No. 368. 



Miehipicoton on the north shore of Lake 

 Superior, present very interesting ex- 

 amples of rock basins. Unlike most of the 

 smaller rock basin lakes of Canada, they 

 are not of glacial origin and probably were 

 not even scoured out by the ice, since they 

 are narrowly enclosed by steep, rocky 

 ridges rising about 150 feet to the north 

 and south and 450 feet toward the east. 

 The shape of the valley is somewhat like 

 that of an armchair with its back to the 

 east, the two ponds, called Boyer and 

 Sayers lakes, occupying the narrow seat. 

 They had a depth of from 125 to 150 feet 

 in the beginning, but Boyer lake, the 

 higher one, is now partially pumped out to 

 facilitate mining operations. From Boyer 

 to Sayers lake the fall is 25 feet; and 

 from Sayers to Talbot lake, which is be- 

 yond the high rock walls of the valley, 

 there is a drop of 75 feet. 



The valley of the two ponds is cut from 

 roeks belonging to the iron range, chiefly 

 siderite and granular silica banded with 

 magnetite or heavily charged with pyrite, 

 and the lowest point of the rim of each con- 

 sists of silicious siderite containing much 

 pyrite. The side walls of the valley are 

 of greenish schists. The hollowing of the 

 basins must have been due to solution, per- 

 haps of parts of the iron range rocks which 

 had been shattered ; and the deposit of the 

 large ore body at the eastern end of Boyer 

 laKe, where a high hill, consisting largely of 

 impure siderite, drops steeply down to the 

 basin, probably has a bearing on their for- 

 mation, the decomposition of pyrite per- 

 haps furnishing the solvent. 



The next paper was : 



The Effect of the Shore Line on Waves: 

 W. M. Davis, Cambridge, Mass. 

 The paper was a statement of the trans- 

 formations of waves as they run in upon 

 shore lines of different forms, with special 

 reference to the refraction of waves on 



headlands and in bays, and to the forma- 

 tion of surf. 



The breaking of waves is not so much 

 due to a retardation by friction of the 

 base of the wave in shallow water, as gen- 

 erally assumed, as to the absence of water 

 in front of the wave near the shore. 



The next paper was: 



Variation of Geothermal Gradient in. 



Michigan: Alfred C. Lane, Lansing, 



Mich. 



The geothermal gradient in Michigan ap- 

 pears to vary from 1° P. in 107 feet to 1° 

 in 54 feet. Among the different causes of 

 variation, the varying diffusivity of the 

 rocks appears to be important. 



Diffusivity varies with the density; the 

 more porous the rock, the smaller the 

 diffusivity. The limestones of Cheboygan 

 have a diffusivity paralleling that of the. 

 copper-bearing rocks of Kewenaw Point. 

 The diffusivity of the shales of Michigan 

 is mdely at variance with that of the lime- 

 stones. 



The next two papers were presented to- 

 gether and illustrated by lantern views: 



Origin and Distribution of the Loess in 

 Northern China and Central Asia: 

 George Frederick Wright, Oberlin, O. 

 Detailed observations in China, Mon- 

 golia, and Turkestan were presented which 

 bear upon the fiuvio-giaeial theory of the 

 origin of the loess of these regions, and of 

 its distribution by wind or water. 



No evidence of glaciation is found where' 

 Geilrie and Krapotkin assumed it. 

 The Age of Lake Baikal: George Fred- 

 erick Wright, Oberlin, Ohio. 

 The region about Lake Baikal is covered 

 with strata of Tertiary (and possibly Trias- 

 sie) age, containing coal. These beds are de- 

 rived from the sediments which were carried 

 by now existing streams into the basin from 

 the surrounding mountains, before the 

 present lake came into existence. At the 



