x March 2, 1882] 
NATURE 
425 
plateaux in the centre of Asia, north of the Karakoram and east 
of the Pamir, are too dry for glaciers, notwithstanding the height 
of the mountains rising over them. ‘The continental parts of 
Eastern Asia (that is China, Maudchooria, the Amoor provinces, 
&c.) have more moisture, but it falls nearly entirely in summer, 
and, owing to the high temperature of the continent at this 
season, rain, and not snow, prevails to the height of 12,000 or even 
15,000 feet. The winter is the time of the north-west monsoon, 
which brings cold but dry weather, with a cloudless sky. The 
monsoon climate of these regions, that is the prevalence of cold, 
dry winds in winter and moist winds in summer, being the result 
of the geographical conditions, it must have prevailed since the 
great features of the centre and east of Asia were as they are. 
The existence of the plateaux and elevations to the south and 
~ west of them is especially important. As all geologists are 
agreed that at least since the Pliocene period this has been the 
ease, I must conclude that the monsoon climate existed in Eastern 
Asia the whole time, and thus conditions exceedingly unfavour- 
able to an accumulation of permanent snow and glaciers. It is 
well known that Pumpelly and Baron Richthofen did not find 
any traces of former glacier action in China or on its western 
and northern borders ; neither did Dr. Schmidt find any in the 
Amoor provinces. Thus geological and climatological evidence 
are perfectly agreed, the first showing that there were no glaciers, 
and the second why there were none. As to the plateaux of 
CentralAsia, they must have been exceedingly dry since the rise 
of the Himalaya and Karakoram to the south and the Pamir 
heights to the west of them, and thus have had nothing corre- 
sponding to the later glacial periods of Europe and North 
America. The geological evidence, especially the studies of 
Stoliczka, confirms this. 
As to the former glaciation of Europe and North America, the 
conditions which must have led to it are, in general, greater 
cold in regions which have now an oceanic climate with heavy 
precipitation, and a more oceanic climate in regions which are 
cold enough, but where the rain and snow are now too deficient, 
especially in the cold season. Great Britain belongs certainly 
to the former class, that is, there is moisture enough, but, owing 
to the warm seas surrounding the islands, the temperature is too 
warm for glaciers. Thus a diminution of the quantity of warm 
water brought from the tropical Atlantic, or a change of these 
currents so as to stop their influence on Great Britain altogether, 
are the principal conditions needful to bring about a heavy 
snowfall, first in the mountains, and then even on more moderate 
heights, and to render the snow persistent. A change of the 
same kind would increase the present glaciers of Norway, 
enabling them to reach the sea even south of the 60° N., and 
give rise to new glaciers. 
It is now pretty certain that all Scandinavia, Finland, North- 
West Russia, and Northern Germany were covered by a sheet of 
ice which gradually filled the Baltic and North Seas and reached 
west of Great Britain, to where the depth of the Atlantic is now 
about 600 feet. Many geologists would have the whole extent 
of country standing much hivher to initiate such an intense gla- 
ciation, I would not objeet to this for the mountainous districts, 
those of Scandinavia especially ; but there is decidedly no proof 
of it for the plains, and the arguments from a climatological 
point are strongly against such a supposition, A rise of less 
than 600 feet in North-West Europe would empty the Baltic 
and North Seas, and extend the Continent to much beyond 
Ireland. This would give to Konigsberg in Prussia a climate 
as continental as that of Orenburg on the borders of the Kirghiz 
steppes.. Such a dry climate would be so unfavourable to per- 
-manent snow and glaciers, that no amount of rise of the land 
would outweigh it. 
I suppose, on the contrary, that a rise of the seas or a sinking 
of the land had very much increased the extent of country 
covered by the sea, and besides giving access to the cold water 
and ice of the Arctic Ocean through what now are the Lakes of 
Ladoga, Onega, and the White Sea, brought a moist and cold 
climate to the whole region. Thus an accumulation of snow 
and ice was brought about first on the highlands, and the ice 
by and by expelled the waters of the shallow seas (the present 
lowlands of North-West Russia, Scandinavia, and North Ger- 
many) and then of the somewhat deeper seas (the present Baltic 
and North Seas). As the ice advanced, the elevation of its 
interior part and the cooling due to the presence of snow and 
ice. counterbalanced the greater distance of the sea, favouring a 
heavy snowfall even in summer, 7.2. giving the conditions which 
now exist in the interior of Greenland. 
; 
Similarly in North America the submersion of a part of the 
Western plains, uniting Hudson’s Bay to the Gulf of Mexico, 
was necessary to the beginning of intense glaciation. A vast 
extent of cold sea was thus called into existence in the West, 
and as the westerly winds are very prevalent and strong there, 
this must have caused a heavy snowfall during the greater part 
of the year. It is known that even now the precipitation of rain 
and snow is very heavy in the United States and part of Canada 
from the Atlantic to the Mississippi, so heavy that it it is un- 
equalled by any extensive region of the globe under the same 
latitudes. Besides, the cold sea to the West went far to prevent 
the influence of the hot and dry summer temperature on the 
plains between the Rocky Mountains and the 100° W. or even 
beyond. American geologists have shown how closely the ice- 
sheet conformed to the present amount of precipitation, there 
being a ‘‘driftless” region in Wisconsin, which is now drier 
than the surrounding country, having less than thirty-two inches 
of precipitation in the year, and of four in winter.! The same 
relation is to be found in the Old World wherever the pheno- 
mena are better studied ; glaciation was more extended in the 
moister Western Alps than in the drier Eastern Alps; it was 
less in the Caucasus and Central Asia (z.e. the part west of the 
Pamir and Thian-Shan) than in the Alps, &c. 
IT have now to consider the possibility of so-called ice-caps 
reaching in an unbroken sheet from the Pole to a latitude of 
45°-50°. All I mentioned before leads to the conclusion that 
they are impossible, as on extensive and deep seas an accumula- 
tion of ice is impossible, as the ice is immediately broken by 
winds, currents, and tides, and on great continents the climate 
is too dry. Thus now there is nothing like an extension of ice 
of that kind in the southern hemisphere, because the greatest 
part of the latitudes above 45° are open ocean, and on the 
northern because the continents are too dry. And the one or 
the other cause always must have prevented an extension of ice 
of a magnitude as stated above, and mostly probably there were 
both too extensive continents and too great and deep oceans to 
allow of an accumulation of ice on a very great part of them at the 
same time. Thus a displacement of the centre of gravity due to 
ice of the magnitude supposed by Mr, Crollon this hypothesis, is 
inadmissible. But one thing is worthy of remark in this hypothesis : 
it is the search for a cause which may explain the changes of the 
level of the sea, which certainly have taken place on the globe, 
and which are now explained as due to. the rise or subsidence of 
the land on the Lyellian hypothesis of the stability of the 
sea-level. 
The influence of a high eccentricity on the accumulation of 
snow and glaciers has next to be considered. This is a question 
which has been considered especially by British geologists, and 
the majority of them agree in attributing a great influence to that 
cause, and in thinking that with the winter in aphelion during a 
high eccentricity there existed conditions favourable to an accu- 
mulation of ice. 
Let us take the simplest conditions, those in the interior 
of a great continent, for example, Asia. Weshould expect then, 
during high eccentricity, a greater cold in mid-winter, and 
greater heat in midsummer when winter is in aphelion. A 
greater cold in winter would not be conducive to an accumulation 
of snow, while a more intense heat in midsummer would pro- 
bably melt the snow at heights where at present temperature does 
not rise much above 32° F. In the monsoon regions a colder 
winter in the interior, with the accompanying higher pressure of 
the air, would intensify the cold and dry winter monsoon winds, 
and thus bring about conditions even less favourable to an accu- 
mulation of snow. Greater heat in summer in the interior of 
Asia would intensify also the moist summer monsoon, and thus 
give a greater amount of precipitation. But owing to the small 
amount of snow falling in winter and its rapid melting, the 
temperature would rise over 32° I'., even at considerable heights, 
greater than now, and the precipitation due to the moist winds 
would be rain, Thus, in the interior and eastern part of a 
continent like Asia, winter inaphelion during a high eccentricity 
would be less favourable than even the present conditions to 
permanent snow and glaciers. 
As to the western parts of continents and to islands, they are 
more fully under the influence of the seas. As there is no 
reason to suppose that the surface-temperature. of the sea would 
be lower during winter in aphelion and high eccentricity, it fol- 
lows that there will not be more snow than now in countries 
where rain is the rule, even in winter, all other things equal, As 
2 A, Dana in S7//. ¥ourn. c. XV. Pp. 250. 
