2 Alexis Perrey on Earthquakes. 
gous maxima and two minima, the maxima corresponding to the 
passage of the superior and inferior meridian, and the minima 
shocks, show that there is a relation between the frequency of 
earthquakes and the rotation of the moon. Is this relation one 
of cause and effect? I believe so, after a careful study of the 
subject, and propose to present the evidence 
Suppose now the envelop or crust to have so great thickness 
and such elasticity that it cannot take at once the form of the 
central nucleus, Pressure and tension in the crust of a greater 
or less amount will be the result, which will be a cause of frac- 
tures. ‘These fractures will be the starting point of molecular — 
vibrations which may be propagated in the crust to its surface _ 
