W. B. Taylor — Crumpling of the Earth's Crust. 259 



spheroidal form due to its rate of rotation, as certainly and 

 promptly as if it were liquid.* 



Granting then that the earth were solidified with an oblate- 

 ness such as has just been assumed, its present dimensions — 

 and probably its present topography — would not be very dif- 

 ferent from what we now find them. 



But another very serious error in the estimates of both these 

 quotations should not be overlooked. While it is quite im- 

 possible to calculate the time when the equatorial radius was 

 one-tenth greater than at present, it is very certain that any 

 estimates based on the existing retardation from the ocean 

 tides, must be utterly fallacious. Not only has this tidal action 

 been continually decreasing (by some small exponent) from the 

 earliest times, but the bodily tides of the liquid or solid earth 

 have undoubtedly played a far greater part than the superficial 

 ocean tides — in the absorption and destruction of its rotatory 

 momentum. f It is not at all probable therefore that it has 

 required " a thousand million years " to effect the present equa- 

 torial contraction of one-eleventh from the former diameter of 

 8,718 miles. 



The much, debated question of the probable degree of rigidity 

 of our planet is therefore quite irrelevant to the problem before 

 us. And yet with so much confidence and persistence has the 

 pet-hypothesis of its entire solidity been maintained, — the 

 temptation is strong to waste upon it a collateral glance. 



Professor William Thomson contends : " Had the solid part 

 of the earth so little rigidity as to allow it to yield in its own 

 figure very nearly as much as if it were fluid, there would be 

 very nearly nothing of what we. call tides, that is to say, rise 

 and fall of the sea relatively to the land ; but sea and land 

 together would rise and fall a few feet every twelve lunar 

 hours. This would (as we shall see) be the case if the geological 

 hypothesis of a thin crust were true. The actual phenomena 



* "However great in a given portion of matter may be the excess of the form- 

 preserving force over the form-destroying force, it is clear that if during augmen- 

 tation of bulk the form-preserving force increases only as the squares of the 

 dimensions, while the form-destroying force increases as their cubes, the first 

 must in time be overtaken and exceeded by the last ; and when this occurs the 

 matter will be fractured and re-arranged in obedience to the form-destroying 

 force." — Herbert Spencer. And the author estimates that "the most tenacious 

 substance with which we are acquainted — when subjected to the same forces that 

 are acting upon the earth's crust — would exceed the limit of self-support deter- 

 mined by the above law, before it attained the thousand-millionth of the earth's 

 bulk."— L. E. D. Phil. Mag., March, 1847, vol. xxx, pp. 194-196. 



f Mr. G. H. Darwin remarks : " Whatever may be thought of the theory of the 

 viscosity of the earth and of the large speculations to which it has given rise, 

 the fact remains that nearly all the effects which have been attributed to the 

 action of bodily tides would also follow (though probably at a less rapid rate), 

 from the influence of oceanic tides on a rigid nucleus." — Phil. Trails. Roy. Soc, 

 Dec. 19, 1878: vol. clxx, p. 538. 



