1869.] GEOLOGY AND MINERALOGY. 79 



depths of 500 fathoms or more, in the ocean westward of Great 

 Britain. This is a proof by actual thermometric observation of 

 a fact on which the writer of this notice has long insisted on 

 other grounds, viz., that cold and dense currents of water fluw 

 over the sea bottom ; and must be taken into the account in our 

 reasonings as to erosion and the distribution of life in the glacial 

 period. Those who have hitherto denied this will now have an 

 opportunity to modify some of their views with regard to Post- 

 pliocene Geology. Other applications of these researches to 

 Geology will be seen in the following extract : — 



" It can be scarcely necessary to point out in detail those various 

 importjint applications of the foregoing conclusions to Geological 

 science, which will at once occur to every Geologist who 

 endeavours to interpret the past history of our globe by the light 

 of the changes it is at present undergoing. But this Eeport 

 would not be completed without some notice of these. — In the 

 first place, it may, I think, be considered as proved that no valid 

 inference can be drawn from either the absence or the scantiness 

 of Organic Bemains in any unmetamorphosed sedimentary rock, 

 as to the depth at which it was deposited. So far from the 

 deepest waters being azoic, it has been shown that they may be 

 peculiarly rich in Animal life. On the other hand, comparatively 

 shallow waters may be almost azoic, if their temperature be low 

 or their currents be strong; and thus even littoral formations 

 may show but few traces of the life that might be abundant on 

 a deeper bottom at no great distance. — Again, it has been shown 

 that two deposits may be taking place within a few miles of each 

 other, at the same depth and on the same geological horizon (the 

 area of one penetrating, so to speak, the area of the other), of 



which the Mineral character and the Fauna are alike different 



that diiference being due on the one hand to the direction of the 

 current which has furnished their materials, and on the other to 

 the temperature of the water brought by that current. If our 

 " cold area " were to be raised above the surface, so that the 

 deposit at present in progress upon its bottom should become the 

 subject of examination by some Geologist of the future, he would 

 find this to consist of a barren Sandstone, including fragments of 

 older rocks, the scanty Fauna of which would in great degree 

 bear a Boreal character ; whilst if a portion of our " warm 

 area" were elevated at the same time with the " cold area," the 

 Geologist would be perplexed by the stratigraphical continuittj of 



