IF. B. Taylor — Crumpling of the Earth's Crust. 251 



There were not wanting some however who questioned the 

 sufficiency of the cause to accomplish the observed results ; 

 and our colleague Captain 0. E. Dutton some ten or twelve 

 years ago with great acuteness pointed out the entire inade- 

 quacy of the " Contractional Hypothesis," from an engineering 

 stand-point.* 



Mr. Robert Mallett, a zealous supporter of the contractional 

 hypothesis, estimated that the diameter of the earth is now 

 about 189 miles less than it was when entirely fluid, f That is, 

 that the surface has collapsed ninety-four miles. Liberal as is 

 this allowance (a surface contraction linearly of ^), it would 

 still be utterly insufficient to represent the actual average of 

 compression. But in point of fact, the whole amount of cool, 

 ing, and therefore of possible contraction by cooling, has been 

 very much less than has generally been assumed.:}: 



1. No permanent crust could have been formed upon the 

 molten globe until convective currents had well nigh ceased ; 

 that is, until the entire mass had cooled down very nearly (say 

 — within a hundred degrees F.) to the congealing point.§ 



2. After the formation of a permanent crust, the greater 

 part of the heat escaping through it would probably have been 

 the "latent heat" from consolidation of new accessions to its 

 inner surface, with little reduction of the sensible temperature 

 of the inner mass. 



3. Whatever expansion by freezing or consolidation of such 

 accessions to the inner surface might occur, would to their ex- 

 tent counteract the effects of interior shrinkage. 



4. The further escape of the encased heat through several 

 miles of so poor a conductor as the earth's crust, must have 

 since gone on with extreme and ever lagging slowness; and 

 even through the lapse of a million centuries, must have been 



*This Journal, 1874, vol. viii, pp. 113-123. The Rev. Osmond Fisher, in his 

 Physics of the Earth's Crust (8vo, Lond., 1881), has also successfully attacked 

 the hypothesis, chapter vii, pp. 73-75. 



f Phil. Trans. Roy. Soc, June 20, 1872, vol. clxiii, pp. 147-227. 



\ " If we were to assign thirty miles as the diminution of the earth's mean 

 radius since the first formation of a cooled exterior, we should probably reach the 

 utmost limit consistent with Fourier's theorem." — G. K Dutton, this Journal, 1874, 

 vol. viii, p. 121. 



§ Mr. William Hopkins, the author of the unfortunate " precession " argument 

 against a fluid earth (or rather against a flexible earth-crust), in the same memoir, 

 well remarks : " If the matter composing the globe was originally in a high state 

 of fluidity from heat, the process of cooling would undoubtedly in the first in- 

 stance be by circulation." And even supposing solidification to commence at the 

 center, he maintains: "The superficial parts of the mass must in all cases cool 

 the most rapidly ; and now (in consequence of the imperfect fluidity) being no 

 longer able to descend, a crust will be formed on the surface ; from which the 

 process of solidification will proceed far more rapidly downward, than upward 

 on the solid nucleus." — Phil. Trans. Roy. Soc. t January 17, 1839, vol. cxxix, pp. 

 381-384. 



