2 S 2 POPULAR LECTURES AND ADDRESSES. 



be practically the same in it as in a solid globe, and 

 that the tides will be practically the same as those 

 of the equilibrium theory. From this it follows 

 that precession and nutations of the solid crust, with 

 the practically perfect flexibility which it would have 

 even though it were IOO kilometres thick and as 

 stiff as steel, would be sensibly the same as if the 

 whole earth from surface to centre were solid and 

 perfectly stiff. Hence precession and nutations 

 yield nothing to be said against such hypotheses 

 as that of Darwin, 1 that the earth as a whole takes 

 approximately the figure due to gravity and centri- 

 fugal force, because of the fluidity of the interior 

 and the flexibility of the crust. Hut, alas for this 

 "attractive sensational idea that a molten interior 

 to the globe underlies a superficial crust, its surface 

 a-itated by tidal waves, and flowing freely towards 

 any issue that may here and there be opened for 

 its outward escape" (as Poulett Scropc called it)! 

 the solid crust would yield so freely to the deform - 



1 "Ob.servalions on the Parallel Roads of (ilen Roy and oilier 



if I.ochaber in Scotland, with an attempt to prove that they 



me . >f marine origin. " Transactions of the Royal Society for February' 



