30 TRANSACTIONS OF THE [OCT. 18, 



self affected by tidal movements, but that it acts as a buffer be- 

 tween the liquid interior and the solid crust. It should be re- 

 membered that the moon's attraction — the chief motor in oceanic 

 tides — is a force applied to a surface moving at the equator about 

 a tliousand miles an hour. Even a fluid as thin as water refuses 

 to obey instantly an attracting body. The tidal wave of the 

 ocean is.always considerably behind the moon, and in some places 

 where obstructed by topographical features it does not reach its 

 destination until some time the next day. It is easy to see that 

 in a tarry, pitchy mass the response to the moon's attraction 

 would be far less prompt, and also that the tidal waves in zones 

 of different depths and densities would not coincide, and might 

 completely neutralize each other. 



Every boy knows that if a flat rock is thrown from a cliff on to 

 water some distance below, it is shattered almost as though it fell 

 upon a solid ; but the velocity of a falling body in vacuo is 16 

 feet the first second, 48 the second, etc., and with the resistance 

 of the air, it is doubtful whether a stone thrown from a cliff 100 

 feet high reaches the water with a velocity greater than 50 feet 

 a second, while the velocity of impact, if we may use the ex- 

 pression, of the moon's attraction is nearly 30 times greater than 

 that, or 1,466 feet per second. The resistance which the internal 

 friction of a viscous body would offer to a force applied with such 

 velocity would be enormously greater. Hence we must conclude 

 that the tidal movement in such a mass even at the earth's sur- 

 face must be very small, and if, as is the case in the interior of 

 the earth, that mass were condensed and constrained by the 

 weight of a crust even a hundred miles in thickness, it would be 

 inappreciable. It should be remembered that the force of grav- 

 ity acting upon a column of matter one foot square and having 

 the density of the materials composing the earth at the surface, 

 that is 2^ times that of water, is 792,000 lbs. for every mile, or 

 79,200,000 lbs. at the depth of 100 miles. Such a pressure must 

 greatly increase the density of matter of any kind. The average 

 density of the earth is 5^ times that of water, and it is plain 

 that in matter of this density and so situated not only a tidal 

 wave would be impossible, but any attraction which is constantly 

 and rapidly changing its j^oint of bearing must be practically 

 powerless to distort the figure of the earth. 



FLEXIBILITY OF THE EARTH'S CRUST. 



It is difficult to imagine how the advocates of the theory of a 

 solid globe can account for the formation of mountain chains, 

 the loftiest and longest of which are quite modern; and it is not 

 perhaps too much to say that these themselves are a refutation 

 of their theory. It is evident that a heated solid globe, as it lost 



