140 Correspondence — Rev. 0. Fisher — Mr. T. Mellard Reade. 



Carboniferous times, and with which the Shap granite is itself 

 connected. 



The metamorphic effects of the granite upon the surrounding 

 rocks are then described. A remarkable set of changes produced in 

 a series of andesites and another of rhyolites, with their respective 

 pyroclastic rocks, is considered in detail, and the results of the 

 metamorphism of the Coniston Limestone series and the Coniston 

 Flags and Grits are given and compared with those obtained by other 

 workers in Norway, the Harz Mountains, and elsewhere. 



COiaE-IESIPOlNriDIBlNrGE - 



MR. OLDHAM ON THE HIMALAYAS. 

 Sir, — It is needless to say how much it has pleased me that Mr. 

 Oldham's knowledge of the structure of the Himalayas confirms in 

 his opinion my theory, published in the " Physics of the Earth's 

 Crust," concerning the formation of a mountain range, and of the 

 effects of its subsequent denudation. I wish, however, to point out 

 that the latter are in my work discussed on the hypothesis that the 

 chief streams are formed, and deposit their sediment, on the less 

 steep side of the range. I had rather the instance of the Andes in 

 my mind as a typical range of mountains. With the Himalayas the 

 case is different. The great rivers, Indus and Ganges, after collect- 

 ing their burden of detritus during long courses between the parallel 

 ridges, finally break through the steep face of the range, and form 

 their deposits on that side. Hence arises the modification of my 

 theory, which Mr. Oldham has found it necessary to make in apply-' 

 ing it to the denudation of the Himalayas. 0. Fisher. 



Harlton, Cambridge, 5 Feb. 1891. 



MR. MELLARD READE AND THE HERSCHEL-BABBAGE THEORY 

 OF MOUNTAIN BUILDING. 



Sir, — The theory of the formation of mountains set forth by me 

 in " The Origin of Mountain Ranges " has been so frequently of late 

 alluded to as a modification of the " Herschel-Babbage" theory, that 

 I shall feel much obliged if one of those who think it so will kindly 

 set forth what the " Herschel-Babbage " theory is. I fear that my 

 friend Mr. 0. Fisher is largely responsible for this description of my 

 theory.^ I have examined his references to the works of Herschel 

 and Babbage, and must certainly repudiate the labelling as a mis- 

 description. There is no analogy between Herschel's view of the 

 elevation of mountains and mine, and indeed by a sort of dramatic 

 justice I find that Mr. R. D. Oldham^ commends Mr. Fisher's work 

 as containing the "most recent and complete adaptation of this (the 

 Herschel-Babbage) doctrine to the theory of mountain formation." 



As a matter of fact, the only element in my theory taken from 

 either of these distingnished men is the law discovered by them that 

 the lines of equal internal temperature in the Earth's crust (isogeo- 



1 Physics of the Earth's Crust, second edition, p. 132. 



2 Geol. Mag. Feb. 1891, p. 73. 



