3oS The American Geologist. May, is98 
seem to ]-)oint to the glacial period having lasted down in 
these regions to. from a geological point of view, quite a 
recent date, one of the most telling being the great poverty 
in both the fauna and fiora in T erra del Fuego in comparison 
with Patagonia. It is difficult to explain why quantities of 
mannnals, reptiles, insects, phanerogamous plants, etc., that 
still survive on the north shore of the Magellan straits, that 
arc only three kilometres in width, are non-existent in Terra 
del Fuego and are represented by other varieties, unless we 
assume that outward circumstances, presumably a cold 
climate, prevented their coming hither until recent times. 
Thus, so far as at present known, the development in a 
geological sense of the Magellan territories proves to present 
a remarkable parallel to that of lands in the same relative lati- 
tude in the northern hemisphere. It is not less evident that 
in many respects the state of the case is the same here as it 
is in New Zealand, even though we are not yet in a position 
to draw anything like a complete comparison between the 
two portions of the globe. It is not possible for me in this 
short paper to bring forward a complete theory in explana- 
tion of these striking analogies between regions so far apart. 
It is a known circumstance that the climate in the northern 
hemisphere during the central part of the Tertiary epoch was 
warmer than now, though the ratio was not everywhere the 
same, and the same would seem to hold good for the southern 
hemisphere also. Towards the close of the same period a 
general deterioration in the climate ensued in all the lands 
round the two poles known to man. and in Europe, North and 
South America, in New Zealand, and in numerous hill dis- 
tricts. The result was the formation of vast masses oi ice. 
How far this can have come about contemporaneously in all 
parts it would be difficult to determine. But even if it was 
only approximately at the same time in the various regions, 
yet all views of the matter that would explain these phenomena 
as purely local must appear highly improbable, and the same 
may be said of the hypothesis set forth by Croll that premises 
that the glacial periods alternated in the north and south 
hemispheres with, in geological computation, but short in- 
tervals between, furthermore the theory about the change of 
position in the earth's axis, in case we regard these variations 
