ADDRESS SECTION A, B.A. 1876. 253 



ing influence of sun and moon that it would simply 

 carry the waters of the ocean up and down with it, 

 and there would be no sensible tidal rise and fall of 

 water relatively to land. 



The state of the case is shortly this : The 

 hypothesis of a perfectly rigid crust containing 

 liquid violates physics by assuming preternaturally 

 rigid matter, and violates dynamical astronomy in 

 the solar semiannual and lunar fortnightly nuta- 

 tions ; but tidal theory has nothing to say against 

 it. On the other hand, the tides decide against 

 any crust flexible enough to perform the nutations 

 correctly with a liquid interior, or as flexible as the 

 crust must be unless of preternaturally rigid 

 matter. 



But now thrice to slay the slain : suppose the 

 earth this moment to be a thin crust of rock or 

 metal resting on liquid matter ; its equilibrium 

 would be unstable ! And what of the upheavals 

 and subsidences ? They would be strikingly ana- 

 logous to those of a ship which has been rammed 

 one portion of crust up and another down, and 

 then all down. I may say, with some degree of 



