and the Origin of Mountain Ranges. 209 



conception. According to a series of experiments made by myself 

 and recorded in the "Origin of Mountain Eanges," the mean 

 expansion of the various rocks of which the earth is composed is 

 about 2'75 feet per mile for every 100° F. This result is well 

 within the mark on comparison with other investigations and, as I 

 use the coefficient throughout, if it be not absolutely correct it will 

 be true for purposes of comparison. 



The linear contraction of 150 miles of rock cooled 1000°, using 

 this coefficient, would be 4125 feet, but, as the contraction of the 

 shell 150 miles deep is voluminal, the contraction in thickness of the 

 shell would be three times this, or 12,375 feet, or=2-344: miles. This 

 would be the radial contraction of the globe from the commencement 

 of the Cambrian, which would give us a circumferential contraction 

 of 77,715 feet, or 14-72 miles. This radial contraction is in excess 

 of what Mr. Osmond Fisher, a well-known mathematician and 

 geologist, has estimated, taking the temperature of solidification at 

 4000° F., for the whole geological history of the globe. ^ I wish to 

 be liberal, and it will serve my purpose. 



We thus have a linear lateral movement or circumferential con- 

 traction in the shell of compression of, say, 15 miles wherewith to 

 build up all our mountain chains and produce the rugosities of the 

 earth's surface that have been created since the beginning of the 

 Cambrian. These rugosities do not all exist now, as they have been 

 planed down again and again by denudation while otherwise grow- 

 ing from age to age. The highest mountains of the earth are of the 

 latest formation, viz. of Tertiaiy age, and it is conceded by most 

 geologists that they are so, not because they were initially higher, but 

 because denudation has not been at work on them so long as on the 

 mountains of preceding periods. According to the greatest estimate 

 of the depth of the level-of-no-strain it is only at the present time 

 5 miles below the surface, so that the mountain-making capacity of 

 the shell of compression ceases altogether at that depth. 



This, of course, is utterly inconsistent with the production of the 

 phenomena of mountain chains, where we find stratified rocks forced 

 up to the surface from much greater depths, and the granitic and 

 gneissic axes, which form a distinguishing feature of all great ranges, 

 give evidence of deep-seated forces acting far below the stratified 

 crust. 



Again, the volcanic phenomena cannot be explained by the lateral 

 pressure of the contracting crust, as these again, it is admitted, have 

 a deep-seated origin. 



When, therefore, we examine this theory of mountain ranges 

 originating from compression of the crust induced by the shrinkage 

 of the globe we prove it quite inadequate to explain the phenomena. 



' Mr. 0. Fisher, taking the temperature of solidification at 4000° F. and the time 

 at 33 million years, arrives at a total radial contraction of 2 miles. If the tempera- 

 ture of solidification were 7000° F. and the time 98 million years, the total radial 

 contraction would be 6 miles. These calculations cover the whole of the time since 

 first solidification, whereas the time I am dealing with is from the beginning of the 

 Cambrian, probably not half the time that has elapsed since the first solidification of 

 the globe.— See Fisher, Phil. Mag. 1888, pp. 7-20. 



DECADE IV. "VOL. I. — NO. V. 14 



