T. Mellard Reade — Origin of Mountains. 413 



and to sink them again, in order to explain a few rounded pebbles 

 on tbe isolated flank of a hill, and make ice travel by some properties 

 unknown to experience over hundreds of miles of level country, 

 scraping the rock as it marches, and yet carrying under its gentle 

 slipper several hundred feet thick of soft clay and sand, and some- 

 times delicate and fragile shells. I do not understand, and feel 

 bound to protest against, the continual appeal of the modern school 

 of geology to causes which have not been verified ; and it seems to 

 me like trying to turn the flank of the north wind by an appeal to 

 the east wind, when a geologist, in order to save a mere scholastic 

 formula, such as Uniforaiity, ignores the laws and conditions of 

 science. 



V. — Some Physical Questions Connected with Theories of the 



Origin of Mountain Kanges. 



By T. Mellaed Eeade, C.E., F.G.S., F.E.I.B.A. 



ME. A. V AUG HAN has honoured with a criticism ^ my 

 exposition of the physical principles upon which my Theory 

 of the Origin of Mountain Ranges is founded, which appeared in this 

 Magazine last May.^ 



Had it not been that much of what I have written seems to 

 have been misapprehended, I should probably have refrained from 

 comment and left the two papers to speak for themselves. 



If Mr. Vaughan will refer to my " Origin of Mountain Ranges," 

 which has been before the scientific public for eight years, he will 

 see that chap, xi., while dealing with " the Hypothesis that Mountain 

 Ranges are ridges thrown up by the Compression induced in the 

 rigid Crust of the Globe by a Shrinkage of the heated Nucleus," was 

 written to show that the ideas then prevailing on the effects of 

 secular contraction were inaccurate, and in this chapter the con- 

 ception of the existence of a level-of-no-strain was first developed. 

 Further, to quote my own words, I say : " If the above reasoning be 

 valid, it is plain that whatever compression may take place in the 

 crust of the globe must be confined to a very slight depth below the 

 surface ; to such a thin stratum, in fact, that the ordinary denudation 

 constantly going on would probably obliterate most of the resultant 

 corrugations." ^ 



In the contrast I have drawn from time to time between my 

 expansion theory, and the older one of secular contraction, I have 

 studiously given the latter theory the benefit of maximum figures in 

 order to prove up to the hilt that the expansion theory gives the 

 most eifective explanation of geological facts as we find them. I 

 join issue with Mr. Vaughan, however, in his calculation of the 

 amount of material which the compression of the outer shell, according 

 to my figures, would give for mountain-making. It would not 

 exceed on the most favourable conditions one twenty-third of the 

 amount he states (p. 316). Also as a practical result such surplus 

 material could not possibly be all used for mountain-making, much 



' Geological Magazine, July, 1894, pp. 312-320. 



2 Ibid. ]3p. 203-214. ^ Origin of Mountain Eanges, p. 125. 



