Dr. W. B. Carpenter on the 



[June 13, 



108. I cannot but regret that an analogy so fallacious should have been 

 put forth by a Physical Geographer of Dr. Petermann's reputation, and 

 should have been adopted by the distinguished author of the 'Prin- 

 ciples of Geology.' A River-current (provided it has an adequate fall) 

 continually increases in strength and volume by the accession of water 

 brought into it by its tributaries ; and the retention of the same name 

 from its principal source to its mouth is therefore perfectly appropriate. 

 But an Oceanic Stream-current, maintained by its initial force alone, tends 

 gradually to diminish in strength, through the retardation it is constantly 

 undergoing by friction, until at last it merges in the general body of 

 water through which it flows. And if that water has a movement of its 

 own, quite independent of any slight residual propulsive force which it 

 may receive from the current discharged into it, nothing but confusion 

 can arise from assigning to it a name which implies that it is as much 

 the continuation of that Stream, as a river at its mouth is of a river at its 

 source. — Of the misapprehension liable to arise from such an inappropriate 

 use of names, I shall now give a notable instance. 



109. Dr. Petermann, after quoting from my Lecture (delivered at the 

 Koyal Institution, February 11, 1870), on the results of the first 'Porcu- 

 pine ' Expedition, a passage in which I express a doubt whether the in- 

 fluence of the " Gulf-stream proper" reaches the European shores of the 

 Atlantic, and citing Mr. Jeffreys as to the evidence afforded by the Arctic 

 character of the Mollusca of this part of the Ocean in disproof of the exten- 

 sion of the Gulf-stream to the coasts of Ireland and Scotland, continues as 

 follows : — " The upper warm stratum of the North Atlantic Ocean, between 

 ** Ireland and the Faroes, was computed, from the soundings of the 

 " ' Lightning ' and the ' Porcupine ' Expeditions, to have a depth of not 

 " less than 700 to 800 fathoms, which, of course, excludes the idea of a 

 " drift or surface- current, and most strongly fortifies the theory of a deep, 

 " voluminous, warm stream. Therefore Carpenter and Jeffreys, while 

 " denying the extension of the Gulf-stream into those latitudes, produce 

 " the strongest evidence against their own assumption." Now it would 

 scarcely be supposed from this reference to my views, that in the sentences 

 immediately preceding and following the one cited by Dr. Petermann, I 

 most distinctly recognized the existence of this " deep, voluminous, warm 

 stream " moving from the South-west towards the North-east ; making its 

 very depth and volume the basis of my argument that it *' cannot be a 

 " continuation of the Florida Gulf-stream, but that it must form part of a 

 "great general movement of Equatorial water towards the Polar area" the 

 complement of " the great general movement of Polar water towards the 

 " Equatorial area, which depresses the temperature of the deepest parts of 

 " the great Oceanic basins nearly to the freezing-point." 



110. Again, in a previous part of the same lecture, I had spoken of this 

 doctrine of a great general Oceanic Circulation sustained by difference of 

 Temperature alone, as one of which Physical Geographers could not recog- 



