1872.] 



' Shearwater * Scientific Researches. 



633 



" slow current," however, is not a mere superficial drift, will appear from 

 the considerations formerly stated (§ 13). 



157. But independently of this general N.E. Oceanic movement, the Tem- 

 perature-observations which have been correlated by Admiral Irminger *, 

 and another series more recently collected and correlated by Prof. Mohn of 

 Christianiaf , indicate that its surface is traversed by bands of somewhat 

 greater warmth. Admiral Irminger specially notes the existence of two 

 such bands, — one of them a little to the west of Fair Isle, which is regarded 

 by Dr. Keith Johnston and Mr. Buchan (on the basis of Prof. Mohn's data) 

 as the axis of this " slow current," its temperature being sensibly higher 

 than the temperature to the west or east of it ; whilst the other, the posi- 

 tion of which is more variable, is met with much further to the westward, 

 sometimes even beyond the meridian of the southernmost point of Iceland. 

 — These bands, the existence of which has been lately confirmed by Von 

 Middendorf (§ 1 60), are regarded by Admiral Irminger (as it seems to me 

 with great probability) in the light of real continuations of the " Gulf- 

 stream proper," which are not only deflected northwards, but also carried 

 onwards by the general N.E. " set." Admiral Irminger, moreover, with- 

 out refusing to the " Gulf-stream proper " some share in the amelioration 

 of the Climate of the regions towards which these bands proceed, distinctly 

 expresses his conviction that this amelioration is mainly due to the heat 

 brought by W. and S.W. winds from the " great and broad Atlantic Ocean." 



158. Having thus found, in the Temperature-phenomena of the British 

 Islands and of the Seas immediately adjacent to them, very decided indi- 

 cations of a general N.E. movement of Oceanic surface-water, we shall next 

 trace the relation of these phenomena to the Thermal condition of the por- 

 tion of the North Atlantic that extends from Newfoundland to the Arctic 

 Sea, as indicated by the course of the Isothermal lines laid down in Dr. 

 Petermann's Gulf-stream Charts for January and July. These show (Plate 

 VII.) in a very marked manner the influence of the Labrador current, which 

 bears southward a great body of Polar ice and glacial water, in depressing 

 alike the summer and the winter Isotherms on the western side of the North 

 Atlantic ; the influence of this current in lowering the temperature of the 

 portion of the Ocean in which it meets the Gulf-stream being probably fully 

 as great as that of the Gulf-stream in raising it. — It is curious to see how 

 sharply the summer Isotherms of 54J°, 50°, and 45^° turn northwards to 

 the east of the Banks of Newfoundland : diverging from one another and 

 from the Summer Isotherm of 60° at intervals which are pretty nearly 

 equal almost as far to the East as the meridian of 30° W. ; but then again 

 trending strongly to the North, so that the summer Isotherm of 54^° crosses 

 the parallel of 60° N. before, by a slight trend to the South, it passes 

 through the Pentland Firth. Thence crossing the North Sea, this Isotherm 

 passes along the coast of Norway as far as Tromso (very near the parallel 



* Journal of the Koyal Geographical Society^ vol. xl. (1870), p. 441. 



f ' Temperature de la Mer entrc l'lslandc, l'Ecosso, et la Norvege,' Christiania, 1870. 



2 z 2 



