Hennessy — Fluid State of Bodies of our Planetary System. 585- 



a force nearly 30 times as great, and yet such mountains are not in 

 the slightest degree flattened down. 



!N"o proof has been ever adduced that any of the great table-lands of 

 the continents have been flattened down in this way. Such masses in 

 Central Asia, could not maintain their height if the solid materials of 

 the earth possessed the plasticity invoked by such speculation as to 

 the earth's figure. 



If rotation would cause a solid sphere to acquire such a figure as 

 that of the earth, then, if the rotation were to cease, the spheroid 

 would change its shape back again, and become spherical. Regarding 

 the earth as a sphere, with an equatorial protuberant zone, then, if it 

 ceased rotating, this zone would be subjected to gravity, acting upon 

 it just as gravity acts on the slope of a mountain, or a gradually ele- 

 vated table-land. As the protuberance is about thirteen miles, and the 

 distance, counted in a meridian to the pole, is nearly six thousand 

 miles, the average slope would be less than in 470. We know that 

 mountains of five miles, and great chains averaging over three miles, 

 remain perfectly free from the smallest squeezing down, as far as we 

 can see, unless what is due to weathering. If chains or elevations 

 whose average slope is at least fifty times as great, and to which the 

 degrading action of gravity is therefore nearly fifty times as great, 

 undergo no collapse, we may be assured that this could not occur in 

 the case of the earth's oblate protuberance if our planet ceased to 

 rotate. 



"While the hypothesis of the former fluidity of the planets fully 

 explains their figures, we see that every attempt on the supposition of 

 soHdity completely breaks down. Attempts at proving the present 

 solidity of the interior of our earth have been shown to be invalid * ; 

 and that member of the planetary system which rules it — namely, the 

 sun — has been long since observed to be chiefly in a fluid condition. 

 The close connexion between the physical conditions of the various 

 members of our system seems to be thus completely verified ; and 

 their former fluid condition may be fairly accepted as an established 

 truth. 



* Comptes renclus for 1868, and 6 Mars, 1871 ; also Nature, v., p. 288, and xv., 

 p. 78. 



