16 A. BLTTT. [NO. 1. 



instance, the centrifugal force becomes altered; because the 

 hardest substance known to us would, exposed to the same forces 

 as act on the earth, reach the limit of elasticity ere it attained 

 one thousand millionth part of the size of the Earth. This de- 

 monstration is in Prof. SchiotJs opinion not maintainable. In 

 any case, I think that Spencer is the first who has expressed 

 the opinion that even the solid Earth is capable of altering its 

 form. In the previously named Lecture, in 1869, Peirce states 

 that the lengthening of the sidereal day has most probably 

 induced an alteration in the form of the Earth. And Principal 

 Dawson states, in his „ Story of the Earth and Man" (London 

 1887 ed. 9 p. 291) that this alteration of form, caused by the 

 lengthening of the day, may probably occur at greater or lesser 

 intervals. As long as the crust of the Earth does not yield, the 

 waters will flow to the Poles, but when the strain becomes so 

 great as to cause the hard crust to crack, the equatorial re- 

 gions will become lowered, and the waters will again flow to 

 the equator. 1 



In Philos. Transact. 1879 parts I— II Prof. G. Darwin has 

 written a Paper, the results expressed in which are, shortly, as 

 follows: he assumes that the Earth possesses a small degree of 

 plasticity, and he estimates the internal friction that the tidal 

 action of the Moon and Sun would produce in such a body. H e 



Similar opinions are expressed by Dr. E. Beyer: „Die Bewegung im 

 Festen" (Jahrbuch der K. K. Geol Reichsanstalt. Wien Vol. XXX 1880 

 p. 543 ff.). 



W. B. Taylor expresses himself in a Paper (Amer. Journ. of Science Ser. 

 Ill Vol. XXX, 1885, p. 249 ff.) „On the Crumpling of the Earth's Cruet," 

 against the doctrine of the contraction of the Earth, and thinks that the 

 lengthening of the sidereal day is the cause of the alterations in its crust. 



A. Winchell I Amer. Journ. 1. c. p. 417) attempts in a Paper „Sources of 

 Trend and crustal Surplusage" to show that the diminishing centrifugal force 

 has produced folds with a North and South direction. 



/. K Todd refers in a Paper geological Effects of a varying Rotation 

 of the Earth" (Amer. Naturalist XVII No 1 January 1883 p. 15 &) fir8t 

 to the various forces acting so as to accelerate or retard the rotation. # e 

 assumes that th- rotation is sometimes accelerated, sometimes retarded, that 



the waters sometimes rise, and sometimes fall, in relation to the land. 



