Reviews — Origin, Growth, and Decay of Mountains. 27 



statement of the subject than is usually presented in geographical 

 text-books". Technical terms have been avoided as far as possible, 

 but a glossary is given in the appendix. The type is bold and clear, 

 and there are few footnotes. 



The author does indeed take a very comprehensive view of his 

 subject. Professor Hobbs, in defining a mountain, remarked that the 

 word is "applied to a feature of the eartli and not merely to an 

 elevated tract", as in the case of high plains; "their summits need 

 not be at great heights above the sea, but it is essential that tbej^ 

 project above the average level of the surrounding country by at least 

 a quarter of a mile." To this or any other definition no strict 

 adherence is made in geographical works, "elevations of the same 

 height being called hills in one locality and mountains in another." 

 The Malvern Hills, for instance, form a true mountain range in point 

 of structure, and, as Professor Geikie observes, even diminutive hills 

 must sometimes be put " into the same class with the loftiest 

 mountains of upheaval ". We find therefoi"e that, in elucidation of 

 his subject, the author more or less briefly describes various mounds 

 and low hills of glacial detritus or wind-borne sand. His general 

 grouping of hills and mountains is : I. Original or Tectonic ; 

 II. Subsequent or llelict mountains. 



The Original or Tectonic mountains are classed as (1) those due to 

 Accumulation, and (2) those due to Detonnation. \Ve are brought 

 first to consider the eminences due to volcanic accumulations, and the 

 subject is illustrated by many text-figures and fine plates. Here it 

 may be mentioned that the terra ' cone-in-cone ' is applied to small 

 and younger cones within a more extensive eroded crater-ring or 

 caldera ; but the term is more usually applied to nail-head spar 

 or fibrous calcite, and to peculiar concretionary and crystalline 

 structures seen in coal. Geyser sinter-mounds, moi'aines and other 

 glacial features, and sand-dunes now come in for attention, many of 

 these being of less altitude than the artificial Silbury Hill or the 

 ' tips ' from mine-works. 



Passing on to the Deformation mountains, we come to the main 

 portion of the subject, one which concerns " nearh* all the more 

 prominent ranges and cliains of the globe ". Three types are 

 recognized, namely. Folded, Dislocation, and Laccolith mountains. 

 The author's object is to give particulars of the geological structure, 

 discussing theories of uplift and the origin of the features, without 

 dwelling much on the scenery. This last-named topic is, however, 

 well illustrated by the beautiful plates, produced mostly from photo- 

 graphs taken for the Scottish branch of the Geological Survey. 



The various types of folding and dislocation are clearly explained, 

 with the aid of diagrams and sections, as well as by photographic 

 views of rock-structures seen in hand-specimens and in exposed rock- 

 masses. Tlie author observes that " To-day the prevalent belief is 

 that deformation of the crust has probably as a rule taken place 

 slowly and gradually, and that erosion and denudation have 

 necessarily accompanied the elevation of mountains, so that through- 

 out the whole period of their growth or upheaval they have been 

 subject to continual degradation ". This is no doubt true enough, 



