8 Proceedings of the Royal Physical Society. 



apparent. But these phenomena are seldom seen, except 

 when found by those desirous to support their Plutonic views, 

 a race of philosophers by no means rare, and who, I am 

 sorry to say, are now occupying the highest places in the 

 science. Formerly these gentlemen asserted that the gra- 

 nite crystallised by slow cooling ; now it is found that this 

 doctrine is untenable, and it must have crystallised by rapid 

 cooling. If this latter view is correct, I ask the supporters 

 of the hypothesis how they explain the fact that the lowest 

 granite differs in no mineralogical character from the upper- 

 most peak of the Himalaya mountains ? Surely the lowest 

 portions of those great ribs on which the foundations of our 

 fair earth were built must have been more highly molten, 

 being so much nearer to their favourite central heat than 

 the upper ranges, and therefore more slowly cooled. By 

 the first view (that is Hutton and Hall's), the lower layer 

 of granite should be more crystalline than the upper, but it 

 is not so. By the more recent theories of Harcourt and 

 others, the upper layer ought to be the more crystalline ; 

 but it is not so, — and on the horns of this dilemma I leave 

 the supporters of Hall, Hutton, and Harcourt. 



The last two dogmas of the new school of geologists are 

 contained in the following words, which I quote from the 

 Kev. Vernon Harcourt's report:— 



1st, " All the consolidated strata, viewed chemically, bear 

 marks of subjection to an action of heat agreeable to the 

 theory of the earth's refrigeration in direct proportion to the 

 age of their deposit ; and that they show that action most ex- 

 plicitly in the presence throughout, but more abundantly as 

 the series descends, of that peculiar form of silica which is che- 

 mically reproduced by the action of heated volatile matter. 



2d, " That the igneous minerals were formed by molecular 

 aggregation at a heat not exceeding perhaps that of an 

 ordinary fire, either as a residuum from the expiration of 

 fusible and volatile materials, or more generally as a deposit 

 from volatile forms of matter." 



These seem very heavy dogmas to deal with ; but before 

 accepting them, it is the duty of every mineralogist and 

 geologist to test them before adoption as a part of their 



