ness of the crust, the nutation would be negative; if the 
period were equal to this second critical value, the nutation 
would be infinite: and if the period were still less, the nutation 
would be again positive. Further, the 183 days period of the 
solar nutation falls so little short of the critical 500 days, that 
greater semi-axis of the approximately circular ellipse described 
by the pole amount to 19x 00885, which is 1-7. It would 
be negative and of some amount between 1’ and infinity, if 
the thickness of the crust were anything from zero to 120 kilo- 
problem is, it cannot afford a decisive argument against the 
earth’s interior liquidity. It assumes the crust to be perfectly 
stiff and unyielding in its figure. This of course it cannot be, 
€cause no material is infinitely rigid; but, composed of rock 
and possibly of continuous metal in the great depths, may the 
ters thick, it would yield very nearly as much as if it were 
Eber, to the deforming influences of centrifugal force 
n coherently worked out, I think I see far enough towards 
4 complete solution to say that precession and nutations wl 
f ae neally the same in it as ina solid globe, and that the 
ides will be practically the same as those of the equilibrium 
