THE ORIGIN OF THE FAUNA AND FLORA OF NEW ZEALAND. 253 
at rare intervals in glacial epochs, and which have been shewn 
to depend upon changes of eccentricity of the earth’s orbit, and 
the occurrence of summer or winter in aphelion, in conjunction 
with the slower and more irregular changes of geographical con- 
ditions; these combined causes, acting chiefly through the 
agency of heat-bearing oceanic currents, and of snow-and-ice- 
collecting highlands.* 
An inhabitant of the southern hemisphere may well ask in 
surprise, “ Where is the evidence for this comprehensive state- 
ment ?” And Mr. Wallace himself, in the ninth chapter of his 
book, argues lucidly in favour of there having been no changes 
of any importance in the climate of the northern hemisphere 
between the triassic and pleistocene periods. All the informa- 
_tion we obtain from Mr. Wallace is the following: “That there 
was such agreater accumulation of ice (in the southern hemis- 
phere) is shewn by the traces of ancient glaciers in the Southern 
Andes, and in New Zealand, and also, according to several 
writers, in Southern Africa, and the indications in all these 
localities point to a period so recent that it must almost certainly 
have been contemporaneous with the glacial period of the 
northern hemisphere.’*t And further on he says, “We may 
further assume that what we know took place within the Arctic 
circle also took place in the Antarctic—that is that there have 
been alternations of climate during which some portions of what 
are now ice-clad lands, became able to support a considerable 
amount of vegetation.”{ This is all I can find in Mr. Wallace’s 
book, and it must be allowed that it is very unsatisfactory. 
Let us therefore try to estimate fairly what the evidence really is. 
The only evidences in the south of former temperatures 
higher than at present, are (1) The miocene fauna which I dis- 
cussed in my former address, and (2) The fossil trees of 
Kerguelen’s Land and the Crozet Islands, which must once have 
formed) part of a luxuriant forest. But at the present time 
Fuegia, which is considerably south of Kerguelen’s Land, sup- 
ports luxuriant forests§ and so also might the Crozet Islands 
and Kerguelen’s Land if they were of larger extent. The in- 
fluence of land in mitigating the effect of the icy ocean is well 
shewn by a comparison of New Zealand with St Paul’s Island, 
in Lat. 38° 10° S., on which the largest tree is only a few inches 
imeyeiameter. Ihe Kerguelen trees. therefore do not imply 
a higher temperature than at present, but only a greater exten- 
sion of land, which we have already seen must at one time have 
existed. Wenow turn to the evidence of cold periods in the 
southern hemisphere, and we will take New Zealand first. 
It was Dr. von Haast who first pointed out that the New 
Zealand glaciers had been far more extensive at some former 
* Island Life, p. 484. te her poks 7 cle p: 490; 
§ Dr. Coppinger says that in the museum of Santiago there is a section of a 
beech tree from Magellan which is more than 7 feet in diameter.—Cruzse of the 
Alert, p. 91. 
