Reviews — Professor W. H. Ilobbs — Earth Features. 327 



deals with the fio;ui'e of the earth and the materials composing the 

 lithosphere, including the formation of crystals. He then passes on 

 to consider the method of formation of rocks, and the contortions, 

 tlirusts, and faults to which they have been subjected. Earthquakes, 

 with many instructive illustrations, and seaquakes ; the rise of 

 molten rock to the earth's surface, and the formation of volcanic 

 mountains by exudation of lava and by ejected materials forming 

 cinder cones, are next considered, the various subjects discussed so 

 far occupying 148 pages. 



More attractive, especially to the general reader, will be the 

 descriptions of earth sculpture, which, including glaciation,- occupy 

 most of the remaining parts of the volume. Interesting are the 

 descriptions of rock-weathering, and the author remarks : " How 

 important is the cover of vegetation in retaining the rock mantle and 

 the upper soil layer in their respective positions, as required for 

 agricultural purposes, maj^ be best illustrated by the disastrous 

 consequences of allowing it to be destroyed. Wherever, by the 

 destruction of forests, by the excessive grazing of animals, or by 

 other causes, the mat of turf has been destroyed, the surface is opened 

 in gullies by the first hard rain, and the fertile layer of soil is carried 

 from the slopes and distributed with the coarser mantle upon the 

 bottom lands. Thus the face of the country is completely transformed 

 from fertile hills into the most desolate of deserts where no spear of 

 grass is to be seen and no animal food to be obtained. The soil once 

 washed away is not again renewed, for the continuation of the 

 gullying process now effectively prevents its accumulation." Illustra- 

 tions are given of a once wooded region in China now reduced to 

 desert through deforestation, and of the ' Bad Lands ' of the Colorado 

 Desert. 



The life-histories of rivers and the travels of underground waters ; 

 the influence of jointed and fractui'ed rocks on the flow of inland 

 waters and on the features produced by marine action (chasms, stacks, 

 etc.), receive attention ; so also the action of sun and wind in arid 

 regions. The rise and fall of land are illustrated by evidences of 

 uplifted sea-caves and notched cliffs, raised stacks and beaches, and 

 by drowned rivers and submerged channels. 



A large part of the work (140 pages) is devoted to glacial phenomena, 

 including particulars of the Niagara Falls, and thus we find a repetition 

 of much of the information and a number of the illustrations that 

 were given in the author's earlier volume before-mentioned. He has, 

 however, prepared the present work with the view of its serving as 

 a guide to scientific students and tourists in J^orthern America and 

 Europe who would take the book with them (they would be unlikely 

 to carry two geological volumes) ; the descriptions and illustrations 

 being selected as far as possible from localities likely to be visited. 

 Prominence is thus given to glaciation because " the larger number 

 of colleges and universities in both America and Europe are 

 surrounded by the heavy accumulations that have resulted from 

 former glaciations ". 



The concluding chapters deal with lake basins, and very briefly 

 with the origin and form of mountains. 



