REVIEWS 389 



surface features of these glaciers, the nature of the ice movement, the 

 temperature of the ice at various depths and its relations to the air tem- 

 peratures, thejamount of surface melting, the possible transference of 

 material|from the surface portion to lower portions, the rates of movement, 

 the advances and recessions of the glacial extremities, and the structure 

 of the ice. There is an accessory discussion of the physiographic changes 

 of the region in Pleistocene and earlier times. 



The points that stand out most in the discussion are those which relate 

 to the precipitation of snow and rain, the effects of climatic cycles on 

 glacial movements, the stratification and granulation of the ice, its shear- 

 ing planes, blue bands, and the possible methods of their development. 

 A notable result is the demonstration by daily measurements of the shear- 

 ing of layers of ice over one another, a phenomenon announced by Cham- 

 berlin as a result of his Greenland observations, but questioned by Russell 

 and others. The conclusions relative to glacial movement lie essentially 

 in the lines toward which the more critical recent studies by different 

 investigators seem to be quite surely tending, a composite mode of motion 

 embracing as factors of varying efficiency granular growth, granular inter- 

 movement, shearing of the sliding planes of the ice crystals, and shearing of 

 the glacial layers over one another. An unsatisfactory flavor is given this by 

 an effort, italicized as though important, to make plasticity mean some- 

 thing which plasticity does not usually mean, for no other apparent reason 

 than to justify the retention of an old term which is likely to be either 

 misleading or meaningless. The movement of the ghding planes of an 

 ice crystal over one another is a plastic movement only in the forced sense 

 that the sliding of cards in a pack, or of boards in a lumber pile, is a plastic 

 movement, and such a movement is better called something else. 



The work is very amply illustrated by excellent photographs and maps, 

 and is an important contribution to glacial science. 



tHjji T. C C 



The Fauna of the Salem Limestone of Indiana. By E. R. Cumings, 



J. W. Beede, E. B. Branson, and Essie A. Smith. Thirteenth 



x\nnual Report of the Department of Geology and Natural 



Resources of Indiana, 1906. Pp. 1 187-1487, 47 plates. 



\i-^ The Salem limestone of Indiana is known generally to geologists and 



business men as the Bedford limestone, receiving its name from the town at 



which are located so many of the large quarries of this formation; but the 



name was preoccupied when given to this limestone, since Bedford had 



