542 TRANSPORTING POWER OF ICE IN THE SOUTHERN HEMISPHERE. 



quate was that cause to explain such widely spread effects ! Doubtless, if the pheno- 

 mena had been rare and confined to one part of Europe, a partial deviation from the 

 ordinary course of nature might explain it ; but how are we to reconcile the position 

 of blocks which had been transported from Savoy to the Jura, or from Scandinavia to 

 the plains of Prussia, with such a method of explanation ? Notwithstanding the at- 

 tempts to apply the iceberg theory generally in aid of the transport of submarine blocks 

 (seeing that in northern latitudes it was a vera causa) , still geologists were wholly un- 

 provided with data to reconcile the former action of ice, in latitudes where it does not 

 now occur, with a former condition of Europe favourable to tropical productions : and 

 this argument was vigorously pressed home by the opponents of the theory. In this 

 state of the subject, Mr. Charles Darwin, who accompanied Captain Fitz Roy during five 

 years throughout the southern hemisphere, returned to Europe, with the knowledge of 

 many novel facts bearing upon this and other geological questions. In his journal du- 

 ring the voyage of the Beagle about to be published, and to some pages of which I have 

 had access, after giving examples in low latitudes in the southern hemisphere, he fairly 

 establishes this proposition : — that an equable climate, probably a direct consequence 

 of a large proportional area of water (a probable condition in the geological case under 

 review) is at the same time favourable to the presence of tropical productions, and to 

 a low limit of perpetual snow, and therefore to the descent of glaciers into the sea in 

 latitudes as low as 46° 40'. (pp. 283 — 285.) Judging from these examples, he infers, 

 that the dispersion of floating masses of ice, with included fragments of rocks, descend- 

 ing from the mountain chains of central Europe, where islands alone formerly prevailed 

 (the case above supposed), might absolutely have been anticipated to have taken place 

 during the period before the present. Referring my readers to the original observations 

 of this clear and powerful reasoner for the details of the phenomena in the southern hemi- 

 sphere, by which his inferences are supported, I will here quote his principal conclusion, 

 drawn from the unanswerable facts, which he ingeniously applies to explain the trans- 

 port of great bowlders. 



" The circumstance of a luxuriant vegetation, with a tropical character so largely en- 

 croaching on the temperate zones, under the same kind of climate that allows of a limit 

 of perpetual snow of little altitude and consequent descent of the glaciers into the sea 

 is very important ; because it has been argued, with great apparent truth, that as there 

 is the strongest presumptive evidence of a gradual cooling down of the climate (or rather 

 of a less favourable state for tropical productions) in Europe, it is most unphilosophical 

 to imagine that formerly glaciers could have acted where they do not now occur. It 

 may be asked, what are the circumstances in the southern hemisphere that produce 

 such results ? Must we not attribute them to the larger proportional area of water ; and 

 do not plain geological inferences compel us to allow, that during the epoch anterior to 

 the present the northern hemisphere more closely approached to that condition than it 

 now does ? We are all so much better acquainted with the position of places in our 



