W. B. Taylor — Crumpling of the Earths Crust. 253 



What solution of this seeming pandox have geologists to 

 offer, after the demolition of the "contraction hypothesis?" 

 As yet none has appeared. It would seem then that the prob- 

 lem must be attacked from a different quarter. 



For a century it had been observed by astronomers that the 

 moon's path exhibited a small acceleration (amounting to about 

 10" or 11" in a century), not accounted for by theory. Laplace 

 investigating the problem, showed that as a result of the secular 

 diminution of the earth's orbital eccentricity, there should be 

 an acceleration of the moon of about 10" in a century. And be 

 announced it as established from a computation of the ancient 

 eclipses that our "sidereal day has not changed by so much as 

 one-hundredth of a second since the time of Hipparchus."* 



That remarkable man, Dr. Julius R. Mayer of Heilbronn, in 

 his very original essay on " Celestial Dynamics " published in 

 1848, showed that as the oscillations of the pendulum require 

 for their maintenance a constant expenditure of power, so 

 equally do the oscillations of the ocean tidal wave. " The mov- 

 ing waters rub against each other, against the shore, and against 

 the atmosphere ; and thus meeting constantly with resistance, 

 would soon come to rest, if a vis viva did not exist, competent 

 to overcome these obstacles. This vis viva is the rotation of the 

 earth on its axis; and the diminution and final exhaustion 

 thereof will be a consequence of such action. The tidal wave 

 causes a diminution of the velocity of the rotation of the earth." 1 ' In 

 the next chapter, discussing the consequence of Laplace's demon- 

 stration of the constancy of the length of the day in historic 

 times. Mayer continued : 4l This result, as important as it was 

 convenient for astronomy, was nevertheless of a nature to create 

 some difficulties for the physicist. With apparently good rea- 

 son it was concluded that if the velocity of rotation had re- 

 mained constant, the volume of the earth could have undergone 

 no change [by loss of heat]. . . . The earth's radius measures 

 6,369,800 meters, and therefore its lengtH ought not to have 

 diminished more than 15 centimeters [6 inches] in 25 centuries. 

 . . . Considering what is known about the expansion and con- 

 traction of solids and liquids by heat and cold, we arrive at the 

 conclusion that for a diminution of one degree [C] in tempera- 

 ture, the linear contraction of the earth cannot well be less than 

 the hundred-thousandth part. . . . The reason why in spite of 

 this accelerating cause, the length of the day has nevertheless 

 remained constant since the most ancient times, must be at- 

 tributed to an opposite retarding action. This consists in the 

 attraction of the sun and moon on the liquid parts of the earth's 

 surface, as explained in the last chapter. According to the cal- 



* Sir John Herschel's Outlines of Astronomy, chap, xviii, sec. 908. (See La- 

 place's Traite de Mecanique Celeste; torn, ii, liv. 5, and torn, iii, liv. 7.) 



