444 Climate of the Glacial Period. (October, 
ecliptic has decreased, and argues that the pole of the 
earth instead of describing a circle around the pole of 
the ecliptic describes a larger one around a point six 
degrees from that centre. It is admitted, and is indeed 
an established fact, that the obliquity is less than it was 
“some centuries ago, but the generality of astronomers are 
agreed that this is owing to the small variation that the 
calculations of Laplace and Leverrier showed to be possible, 
and that it is simply a coincidence that the path described 
by the pole is that of a larger circle around a point a little 
distant from the pole of the ecliptic. They contend that 
the pole of the earth does describe a circle around the pole 
of the ecliptic as a centre, but that the outline of that circle 
is a waved one, and that during the time that observations 
have been made the direction of the pole has been down 
towards the trough of one of these waves, but that it will 
again rise as much above as it dips below the mean distance 
from the centre. It is an obje¢tion to this theory as well as 
to that of Lieut.-Col. Drayson that it is assumed that the 
pole of the earth describes a circle, whereas amongst the 
heavenly bodies we have no circular movements. All the 
orbits are ellipses of varying eccentricity, and from analogy 
we should be led to expect that the pole of the earth would 
not describe an exact circle. That it does so is entirely 
theoretical, founded on calculations based on the assump- 
tion that the earth’s equatorial circumference is a circle, 
which it is not. Lieut.-Col. Drayson has informed me that 
though he has assumed the curve to be that of a circle, the 
earlier observations cannot be sufficiently relied on, and it 
may be that of an ellipse or of a spiral. 
Until astronomers have re-considered this question with 
the light of our present knowledge of the figure of the 
earth, geologists should not be prevented from speculating 
on the possibility of great changes in the obliquity of the 
ecliptic having caused former great variations of tem- 
perature. According to Lieut.-Col. Drayson, the obliquity 
of the ecliptic has been as much as 353. ‘The effect of this 
was, he urges, the production of the Glacial period. He 
states that as the arctic circle would then reach nearly to 
latitude 543°, there would be an accumulation of snow 
during the winter; which during the summer, in consequence 
of the great altitude of the sun, would be melted nearly to 
the poles, occasioning enormous floods. Now if this really 
would be the effect of a greater obliquity of the ecliptic, we 
might at once dismiss it as a possible cause of the accumu- 
lation of ice in the glacial period, for it is evident that the 
