Cause of the Glacial Period 
with that of the present day ; and if, in addition to this cause of increased cold, we add that arising from 
a reduction in the temperature of the Gulf Stream, we seem to be warranted in coming to the conclusion 
that such physical conditions would have brought about a glacial climate in this region. 
Region of the Mediterranean, Southern Europe, and Western Asia.—It may be objected that the hypothesis 
here advocated is insufficient to account for the colder conditions of climate which affected Southern 
Europe and the regions bordering the Mediterranean and extending eastward to the Himalayas. 
Throughout all these regions we have evidence that the climate was colder than at present during the 
Pleistocene period, resulting in the extension of the glaciers in the Alps, the Pyrenees, Caucasus, and the 
Himalayas themselves ; while, as the late Sir Joseph Hooker has shown, glaciers were formed amongst the 
mountains of the Lebanon from which they are now altogether absent.! 
To this objection there may be offered two very forcible answers. Frst—It may be confidently 
asserted that a general lowering of the temperature and change in the climate of Western Europe would 
necessarily produce some effect in the same direction on the regions lying beyond. If the climate of 
Scandinavia, of the British Isles, of France, Spain and Portugal became sensibly more rigorous, it is clear 
that owing to the circulation of the air currents the climate of the adjoining regions to the eastward would 
also experience at least a proportionate change in the same direction owing to the greater accumulation 
of ice and snow in the higher altitudes. It is impossible to say to what distance this influence would 
extend, and did extend, during the Pleistocene period, especially during the epoch of maximum cold. I 
think it may safely be assumed that none of the regions above enumerated were altogether unaffected by 
it; and for my own part I am inclined to believe that the entire Northern Hemisphere felt the loss of heat 
due to the diminution of temperature of the Gulf Stream. Second.—But there remains a still more potent 
cause for the greater prevalence of glacial conditions than is the case at present in the regions referred to. 
It has been shown (Chapter VII.) that towards the close of the Pliocene period the vast tract embracing 
the basin of the Mediterranean and adjoining regions extending eastward was undergoing gradual changes 
as regards the relations of land and sea. After a slight depression—during which sea-beaches were formed 
along the old coast-lines in the lands bordering the Levant, there ensued a process of elevation ultimately 
resulting in the conversion of the Mediterranean basin into a chain of fresh-water lakes connected by rivers 
with the Black Sea, and closed against the influx of the Atlantic waters by the uprise of the sea-bed at the 
Strait of Gibraltar. At this period Sicily was connected with Malta and Tunis, while the island was 
inhabited by elephants and hippopotami, as shown by Leith Adams and Spratt. The two lakes thus 
formed were connected by a river channel crossing the “ Medina Bank,” which is now submerged to a 
depth of 250 fathoms.’ Without going further into this very interesting subject it must here suffice to 
state that owing to the uprise of the whole region to the extent of 1200 to 1500 feet (200 to 250 fathoms) 
large tracts now under water were converted into land, and the adjoining areas were upraised land... This 
uprising of the land necessarily brought certain mountainous tracts within the limits of the snow- 
line—as was the case in the Lebanon, where, as already stated, glaciers were formed which have 
left their old moraines at a level of 4000 feet above the present surface of the Mediterranean ; 
mountainous regions such as the Caucasus, where perennial snow lies, were subjected to a more rigorous 
climate. That this general elevation of the Mediterranean and Syrian region extended much farther 
eastward cannot be doubted—how far it is impossible to say ; but there does not appear to be any reason 
why its influence may not have been felt as far as the Himalayas, where, as we know from the observa- 
tions of Hooker, the glaciers once descended far below their present limits. In all these considerations 
we must remember that the two possible causes—those of reduced temperature and of land elevation— 
1 Hooker, “On the Cedars of Lebanon,” Nat. Hist. Rev., 1862 ; also, Sir W. W. Smyth, Pres. Address Geol. Soc. (1868), Quart. Fourn. 
vol. xxiv. p. 58. While these pages are passing through the press, the venerable form of Sir Joseph Dalton Hooker has passed away in his 95th year. 
As a scientific traveller who has revealed to us the glorious flora of the Himalayas and other Eastern countries, Hooker will ever be held in grateful 
remembrance by all lovers of Nature. 
2 Spratt, Quart. Fourn. Geol. Soc. vol. xxiii, p. 292. 8 Hooker, Himalayan Fournals, vols. i. and ii. (1855). 
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