470 Transactions.—Geology. 
Arr. LXXIT.— Further Remarks as to the Cause of the Warmer Climate which 
existed in high Northern Latitudes during former Geological Epochs. 
By W. T. L. Travers, M.H.R., F.L.S. 
[Read before the Wellington Philosophical Society, 17th November, 187 i] 
Ir will be remembered that I had the honour of reading a paper before this ' 
Society in August last, in which I ventured to urge that the warmer climate 
which unquestionably prevailed in high northern latitudes during former 
geological periods, as evidenced by the character of their fauna and flora, 
was chiefly due to the radiation of heat conducted from the interiór to the 
surface of our globe. Since then I have had an opportunity of studying 
Mr. Croll's great work on * Climate and Time," in which that gentleman 
expresses his dissent from all such theories, and endeavours to show 
that the better climatal conditions in question were indirectly due to 
changes in the eccentricity of the earth's orbit, resulting in alternations of 
cold and warm periods at irregular intervals, brought about through the 
medium of heated ocean currents impelled towards high latitudes under the 
operation of the trade winds. To those who have had the advantage of 
studying Mr. Crol's work, it will, undoubtedly, appear presumptuous on 
my part to dispute the conclusions he has arrived at, and still more so to 
maintain a proposition at variance with his opinions, but I venture to think 
that in his treatment of the question he has overlooked some points of 
great importance with which I propose to deal in this paper. But before 
alluding to those points let me call your attention briefly to the views 
which Mr. Croll propounds. 
In the first place he calls attention to the changes which constantly take 
place in the eccentricity of the earth’s orbit, and points out that when this 
eccentricity is at its superior limit (—:0721) the difference in the distance of 
the earth from the sun when in the aphelion, as compared with the peri- 
helion of its orbit, is upwards of 14,000,000 of miles, and that the amount 
. of heat received by the earth when in those two positions will be as 19 to 
26. He next points out that if, according to the precession of the equinoxes, 
winter should happen in the northern hemisphere when the earth was in 
the aphelion of its orbit, at the time when the orbit was at its greatest 
eccentricity the difference in the amount of direct heat received from the 
sun would be sufficient to bring about a recurrence of the glacial epoch. On 
the other hand he urges that if, under the same circumstances, winter were 
to occur in the northern hemisphere when the earth was in the perihelion 
of its orbit, the difference between winter and summer in the latitude of 
England, at all events, would be almost annihilated, whilst extreme glacial 
2 conditions would be transferred to southern latitudes. 
