252 W. B. Taylor — Crumpling of the Earth? s Crust. 



largely compensated by the frictional heat continually generated 

 by the tidal waves in the superior layers.* 



Indeed we may venture the opinion that the ultimate refrige- 

 ration of a body like the earth must require a period of time 

 whose curve would be almost hyperbolic to the asymptote ; 

 and that the entire solidification of a planet has not yet oc- 

 curred in the solar svstem. Even our Moon, with a mass less 

 than one-eightieth of our own, and with an exterior cooled 

 probably below the freezing point of mercury, may still be 

 very hot if not partially molten within. f 



The volumetric contraction of our globe since the formation 

 of its crust may therefore be regarded as practically very 

 insignificant. On the other hand if we attempt to form an 

 idea of the amount of average shortening of the strata in a 

 given zone about the earth, from the amount of corrugation 

 and displacement observed (assuming from the analogy of sub- 

 marine contours that a corresponding degree of compression 

 exists throughout the ocean beds), an allowance of one-eleventh, 

 or of a primitive excess by one-tenth of the present girth, 

 would probably not be regarded by the geologist as an undue 

 assumption. Professor Alphonse Favre of Geneva in detailing 

 some experiments to reproduce by lateral compression in layers 

 of tenacious clay, the plications of strata, has estimated a linear 

 contraction of one-third, as exhibited by portions of the Swiss 

 Alps4 Our own Appalachians and western Sierras probably 

 indicate as great an amount of shortening. 



But an expansion of the circumference of a sphere by one- 

 tenth, involves an increase of its volume of one-third ; of course 

 a wholly inadmissible assumption on any hypothesis of the 

 formation of a crust. The conception of a gaseous or vaporous 

 intumescence of a body like the earth may be dismissed at once, 

 as simply opposed to physical possibility. § 



* Mr. George H. Darwin has estimated that the internal heat developed by 

 " the lengthening of the sidereal day from 5h. 36m. to 23h. 56m. would be suffi- 

 cient (if applied all at once) to heat the whole mass about 3000° F., supposing 

 the earth to have the specific heat of iron." — Phil. Trans. Roy. Soc, Dec. 19, 1878, 

 vol. clxx, pp. 495 and 535. And in a subsequent memoir, computing this past 

 transformation of energy as equal to thirteen and a half times the whole remain- 

 ing kinetic energy of the present rotation, he arrives at the somewhat startling 

 conclusion : " Thus it appears that at the present rate of loss, the internal fric- 

 tion gives a supply of heat for 3560 million years." (Same volume, pp. 561 and 

 592.) He infers however that only about one-fiftieth of the present downward 

 increase of temperature is referable to the past internal friction. 



■j- This is of course in very strong antagonism to the conclusions reached by 

 Sir "William Thomson's elaborate calculations. 



$La Nature, Sept. 28, 1878, vol. vi, part ii, pp. 278-283. A full abstract of 

 the paper is given in Nature, Dec. 5, 1878, vol. xix, pp. 103-106. 



§ This suggestion is broached by Mr. Fisher in his Physics of the Earth's 

 Crnst, and appears to be in some sense maintained in a recent German work (not 

 seen by the present writer), on Terrestrial Physics (1884), by Ton Siegmund 

 Giinther. 



