384 Notices respecting New Books. 



and conditions of the movable mixture of mud, sand, and stones, 

 that grind and are ground on a glacier's floor, until they find exit 

 at the termiual moraine, or are taken off by icebergs to form 

 submarine till. If the maxima, or even the existence, of ice- 

 sheet periods are to be calculated according to the extent and 

 thickness of such supposed boulder-clay floors (hundreds of feet 

 thick), the calculations must be erroneous : whilst doubtless the 

 distribution, by river, lake, and sea, of the clay and stones 

 resulting from the grinding work of the glaciers simply and 

 satisfactorily meets many of the geological requirements. 



A very large amount of instructive geological detail, obtained 

 by personal research and from a variety of sources, is arranged 

 systematically in treating of stratified and other formations whose 

 origin was in any way associated with periods of extreme cold and 

 with milder intermediate times, — for Scotland (as we have seen) 

 in Chapters II. to XXIII. ; for England in Chapters XXIV. to 

 XXVII.; and for Ireland in Chapter XXVIII. The amount of 

 information collected for Europe (Northern, Middle, Alpine, 

 and Western) in Chapters XXIX. to XXXVI. is extensive, and 

 is carefully arranged; resulting (pages 607-615) in the Author's 

 determination of six glacial epochs, each with its sequent interglacial 

 period ; the last of the latter exists at present time. 



He supports this frequency of climatal changes by reference to 

 his interpretation of successive glacial and non-glacial deposits, 

 and the concomitant topographical modifications in the outlines, 

 heights, and depths of land and water. These being more 

 numerous and complicated than they were thought to be when his 

 earlier editions were published. 



A careful study of the many published accounts of the nature, 

 extent, and origin of the Loess or Lehm is given in Chapter 

 XXXVIII. This Pleistocene deposit is described as a fluvio- 

 glacial inundation-deposit, largely modified and rearranged by 

 wind, snow, and dust-storms, and naturally containing multi- 

 tudinous mammalian bones, many land- shells, and other rarer 

 fossil remains. It necessarily constitutes an important link among 

 the results of the dying ice-age, and the gradual disappearance of 

 the glaciers. 



The advent of a cold climate was indicated for Europe in the 

 Pliocene times ; and the maximum of cold occurred in the " Second 

 Glacial Epoch." Then the alternating cold and temperate periods 

 successively declined in importance. Palaeolithic Man is regarded 

 (p. 689) as having appeared in Europe in Pleistocene times, 

 probably not before the " Second Interglacial Epoch " {Elcphas- 

 antiquus stage) ; and, surviving the " Third Glacial Epoch," he 

 probably retired to Southern Prance, and to Switzerland and the 

 country of the Danube. 



Respecting the relative chronology of the Glacial Epoch and the 

 appearance of European Man, it may be well to note that Dr. Croll 

 at first suggested that the beginning of the Glacial Period may 



