Dr. Carpenter on the Physical Cause of Ocean- currents. 361 



(]) this enormous mass of glacial water, of which, across the 

 whole breadth of the South Atlantic, the lowest stratum of 500 

 fathoms has an average temperature below 35°, exerts no cooling 

 influence on the Intertropical area, and that (2) it can have been 

 propelled thither by the agency of the Gulf- stream or of any 

 other superficial wind-currents, seem to me propositions equally 

 opposed to common sense. 



2. That Polar water is met with at a much less depth under 

 the Equator than it is in the extratropical zone, seems a clear in- 

 dication that it is continually rising there from the bottom towards 

 the surface, as would of course be the case on the theory of a 

 Vertical Oceanic Circulation ; and this inference is strikingly 

 confirmed by the fact (which is diametrically opposed to an- 

 other of Mr. Croll' s assertions, p. 100), that while the salinity 

 of the fo/fom-water maintains its low Polar standard as far as 

 the Equator, and while the salinity of extratropical surface-water 

 is considerably higher, the salinity of Equatorial surface-water is 

 as low as that of the Polar bottom-water, 



3. Of the Polar-Equatorial flow thus evidenced, a poleward 

 flow of the whole upper stratum is a necessary complement; and 

 the observations made by my colleagues and myself between 

 Lisbon and the Faroe Islands, indicate that the thickness of this 

 north-moving stratum is there not less than 700 fathoms; 

 whilst the course of Dr. Petermann^s isothermal lines clearly 

 shows that it extends all across the Atlantic to Newfoundland, 

 where the summer isotherms turn almost due north. That this 

 vast body of water can be propelled by the vis a tergo of the 

 true Gulf-stream (which off Sandy Hook has a breadth of about 

 60 miles and a depth of 100 fathoms), I have not heard of any 

 one but Professor Wyville Thomson, Mr. Croll, and Dr. Peter- 

 mann, who would seriously assert. That it exerts no heating in- 

 fluence, not even Mr. Croll would affirm. 



4. That the real Gulf-stream, or Florida Current, reaches 

 North-western Europe, is a pure assumption of geographers and 

 meteorologists, to account for the abnormally high temperature 

 brought thither by the sea. On evidence which no one has 

 disproved, it may be affirmed that the real Gulf-stream dies 

 out, i. e. loses all the distinctive characters of a current, in 

 the Mid-Atlantic. On the other hand, a vera causa satisfactory 

 to Physicists has been shown to exist for the poleward move- 

 ment of the entire upper stratum. And thus Professor Mohn, 

 of Christiania, in sending me his work ' On the Climatology of 

 Norway' (1872), which assigned to the Gulf-stream the mild 

 winter of the Norway coast, informed me that if he had been 

 acquainted with my latest Report he should have expressed 

 himself very differently, being now satisfied that this ameliora- 

 tion is produced, not by the Florida Current, but by the General 



