1872.] 



'Shearwater' Scientific Researches. 



599 



winter climate of Naples and that of New York, — even going so far as to 

 affirm that the Gibraltar Current is a branch of the Gulf-stream carrying 

 its heat into the Mediterranean, although Thermometric evidence shows 

 that the Gibraltar Current rather reduces, than raises, the temperature of 

 that inland sea. 



99. The doctrine of the extension of the Gulf-stream proper to the 

 Polar area, carrying with it a vast amount of Equatorial heat, has been 

 advocated with great ability by Mr. James Croll ; who, employing the 

 modern method of computing units of heat, essays to prove that the quan- 

 tity of heat carried from the Equatorial area by the Gulf-stream is so 

 enormous, as to be competent not only to do all that Dr. Petermann attri- 

 butes to it, but a great deal more*. In this, indeed, he goes far beyond 

 Dr. Petermann himself ; for, as will presently appear, Dr. Petermann 

 regards the Florida Stream as furnishing only a part of the thermal power 

 exerted by the vast body of water derived from various sources, to which 

 he gives the name " Gulf-stream." 



100. Without attempting to follow Mr. Croll through his calculations, 

 I may stop to point out what appear to me to be the fallacies of his 

 method ; since if this can be proved erroneous, Mr. CrolPs great array of 

 figures is utterly valueless. 



101. In the first place, in Mr. Croll's preliminary comparison of the 

 Temperatures of the Northern and Southern Hemispheres, he altogether 

 ignores the influence on the Distribution of Heat over the Globe which is 

 exerted by the great relative preponderance of Land in the Northern Hemi- 

 sphere. Yet of the vast importance of this influence, no Meteorologist 

 or Physical Geographer can entertain the smallest doubt. The manner in 

 which it affects the relative Temperatures of the North and South Atlantic 

 will be hereafter shewn (§ 118) to be precisely conformable to that in which 

 it manifests itself in the Climates of Continental Stations ; and to affirm, as 

 Mr. Croll does, that " the lower mean Temperature of the Southern Hemi- 

 " sphere is due to the amount of heat transferred over from that Hemi- 

 " sphere to the Northern by Ocean-Currents," is to repudiate all that has 

 been established by the researches of Meteorologists, as to the relative 

 effects of Land and Sea, not only upon Temperature, but upon Atmospheric 

 Vapour, Barometric Pressure, and the prevalent Direction of winds, — in 

 all of which particulars the contrast between the Northern and Southern 

 Hemispheres is so marked, that any transfer of Heat from the latter to the 

 former which can be fairly attributed to Ocean-currents, must be com- 

 paratively insignificant in its effects. 



102. Secondly, in computing the Heat imparted by the Sun to the 

 Equatorial area from which the Gulf-stream is fed, Mr. Croll assumes 



* See his Papers " On Ocean-currents," parts r. and nr., in Philosophical Magazine, 

 Feb. and Oct. 1870; and " On the Influence of the Gulf-stream," in Geological Maga- 

 zine, April 1SG0. 



VOL. XX, 2 X 



