175 
explains the polar land area and the antipodal position of 
nearly all the land to water areas. And he shows that the 
effect of a change of position of the axis with the unequal 
diameters of the earth, which are unequally divided by the 
centre of gravity, will he to cause the land to he antipodal 
to the water, and the slight exceptions are near to the 
circumference, dividing the glohe into land and water hemi- 
spheres, which is where the exceptions would he expected. 
By these exceptions he concludes that the poles have 
moved in a curved direction. If we divide the earth hy a 
plane (grand circle polaire) perpendicular to the equator 
and to the direction in which the position of the poles have 
been changing, the points of intersection at the equator 
form two pivots for this motion, and here the effect of re- 
adjustment will be a minimum, while before and behind 
will be an area of elevation and submergence respectively. 
If the motion is curved, the plane {g.c.jp.) we have just sup- 
posed must cut the tangent of this curve at right angles. 
The changing position of this tangent changes the position 
of the plane, and the points of intersection are removed 
from the elevation to the submergence area on one side, and 
the opposite points from the submergence to the elevation 
area, so that land antipodal to land is the consequence. 
MICROSCOPICAL AND NATURAL HISTORY SECTION. 
February 12 th, 1877. 
W. Boyd Dawkins, F.R.S., President of the Section, in 
the chair. 
Contributions to the Life History of A cidalia Contiguaria 
(Hiibner), communicated by Joseph Sidebotham, Esq., 
F.R.A.S, 
