268 J. Crol—Geological Climatology. 
sary result from an increase of eccentricity. Now if all our. 
mountain summits were covered with permanent snow down 
to a considerable distance, the valleys would soon become 
filled with local glaciers. In such a case we should then have 
more than one-half of Scotland, a large part of the north of 
England and Wales, with nearly the whole of Norway covered 
with snow and ice. ere a new and powerful agent would 
ome into operation which would greatly hasten on a glacial 
condition of things. This large snow and ice-covered surface 
would tend to condense’ the vapor into snow. It would dur- 
ing summer chill the air and produce dense and continued 
fogs, cutting off the sun’s rays and leading to a state of things 
approaching to that of South Georgia, which would much 
retard the melting of the snow. 
t is a great mistake, as I have repeatedly shown, to sup- 
pose that the perihelion summers of the Glacial epoch could 
he hot. No snow and ice-covered continent can enjoy a hot 
summer. This is clearly shown by the present condition of 
Greenland. Were it not for the ice the summers of North 
Greenland, owing to the continuance of the sun above the hor- 
izon, would be as warm as those of England ; but, instead of 
this, the Greenland summers are colder than our winters, an 
snow during that season falls more or less nine days out of ten. 
But were the ice covering removed a snow shower during sum- 
mer would be as great a rarity as it would be with us. On 
the other hand, cover India with an ice sheet, and the sum- 
mers of that place would be colder than those of England. — 
When the high grounds of Scotland and Scandinavia, with 
those of the northern parts of America, became covered with 
snow and ice, and the eccentricity went on increasing, a dimi- 
nution of the Gulf Stream and a host of other physical agencies, 
all tending toward a glacial condition of things, would be 
brought into operation. This would ultimately and inevitably 
lead to a general state of glaciation without the aid of any 0 
those additional geographical changes of land and water which 
some have supposed. This will be shown more fully when we 
come to examine Mr. Alfred R. Wallace’s theory. 
The Mutual Reaction of the Physical Agents.—Those who 
think that the agencies to which I refer would not by them- 
selves bring about a glacial condition appear to overlook @ 
most important and remarkable circumstance regarding their 
- mode of operation, to which I have frequently alluded 10 
‘Climate and Time’ (pp. 74-77) and other places. The cir- 
cumstance is this, The physical agencies in question not only 
] lead to one result, viz: an accumulation of snow and ice, 
but their efficiency in bringing about this result is actually 
