T. B. Struthers — Granite. 561 



Again, I have been compelled to call in the action of water, 

 either as slowly moving rills, as rivers in flood, or filling tundra- 

 like depressions to explain some of the observed phenomena, espe- 

 cially the basal stratification. Nevertheless, the other facts pointing 

 to a different conclusion are too numerous to allow me to accept 

 Prof. Armachevsky's views, and regard the whole deposit as due 

 to the action of atmosj)herio waters. 



Lastly, I have attempted to review the chief physical influences 

 acting on the region at the present day, and conclude therefrom that 

 the actual condition of the Russian Loess is due to a multiplicity of 

 causes, which have been acting (with greater force, perhaps, in 

 former centuries) through a very long period of time. Not the 

 least of these, as explaining the abundant land fauna and the 

 vertical distribution, is the wind which has full play on the boundless 

 Steppe. 



I also trust I have pointed out that behind the origin and 

 distribution of this great deposit lie questions of physical geography 

 of the greatest interest, questions which alone can be solved by a 

 careful and detailed special examination of the country dealt with 

 in these pages. 



VIII. — Granite. 



By Thomas K. Struthers ; 



Hon. Assoc, and late V.P. Geol. See. Glasgow. 



ri'^HE commonly accepted theory of the origin of granite is that, 

 X in view of indications that it had been subjected to great 

 pressure, it was formed deep in the earth's crust in a molten state, 

 and, after consolidating, thrust up through it, or exposed at the 

 surface by denudation. This theory is not altogether satisfactory, 

 being equivalent to an assertion that a stately building was first 

 constructed and its foundation laid afterwards. Like some other 

 unsatisfactory theories, it has been so often reiterated that it is 

 tacitly assented to as authoritative, on the principle, we suppose, 

 that what everybody says must be true. There are existing con- 

 ditions analogous to those under which the trappean rocks were 

 formed, as illustrated by modern submarine and subaerial erupted 

 rocks ; but the conditions under which primitive granite originated 

 are not now represented in any part of the world. There is little 

 difiSculty in tracing the inorganic constituents of all rocks back to 

 granite ; but there is no proof that granite was derived from any 

 pre-existing rock. 



According to Hutton, the fundamental rock of the earth's crust 

 consists of the reunited debris of older continents, which in like 

 manner may have been formed of the reconstructed wrecks of 

 anterior terrestrial areas, and so on backward ad infinitum. In 

 interpreting Button's theory Sir Charles Lyell, in his " Principles," 

 attributes to him a belief that " alternate periods of general dis- 

 turbance and repose had been, and would for ever be, the course of 

 nature." We do not, however, suppose that Hutton meant to insist 

 on this illogical hypothesis, and as it was based only on assumed 



DECADE III. — VOL IX. NO. XII. 36 



