1872.] 



' Shearwater 9 Scientific Researches. 



629 



15° W., where subsequently, in August 1 785, it only showed 66°. Further 

 west, in the course of the Gulf-stream proper, great diversities are obser- 

 vable between the temperatures found at the same points in corresponding 

 periods of different years *. — On the whole, then, it seems probable that the 

 Gulf-stream varies considerably from time to time in force and in heating 

 power ; and that an extension of it into the Bay of Biscay may be sometimes 

 distinguishable by local elevation of the Thermometer, although the ordi- 

 nary temperature of the Atlantic as far north as the British Channel is in 

 no wise dependent on its influence. 



151. Evidence of amelioration in the Climate of the British Isles, and 

 of the region still further North, by a North-easterly flow of Oceanic 

 water. — It is when we pass northwards along the western shores of 

 Europe, as far as the British Isles, that we first encounter, in the marked 

 northward tendency of the Isothermal lines, especially in winter, an 

 indication of northerly movement in the water of the North Atlantic. 

 But it is important here to observe that the winter Isotherms of 55° 

 and 50°, as laid down in Dr. Petermann's Charts, reach a considerably 

 higher Latitude in the Meridian of about 25° W. than they do where 

 they approach the coast of Europe in the Meridian of 10° W., — the 

 former, which nearly touches the parallel of 50°, turning south to Co- 

 run n a in 44° N. Lat. ; and the latter, which rises on that meridian to 54^° 

 N. Lat., falling to 50° at the entrance of the British Channel. Now 

 this may be taken as a very significant indication that the residual heat 

 which the Gulf-stream may retain, after encountering the Arctic Current, 

 is dissipated in the further passage of its water to the eastward. And the 

 same inference may be drawn from the monthly averages of the observa- 

 tions of surface-temperature taken on board the Cunard Steam-ships 

 between the South of Ireland and the Banks of Newfoundland ; which show 

 that while the winter (February) average only falls from 54° in W. Long. 

 40° to 53° in W. Long. 25° (although most of the change of Latitude 

 occurs in that part of the course), it is reduced to 50° in W. Long. 10°. 

 But the winter Isotherm of 45°, like the summer Isotherm of 55°, tends so 

 continuously to the North, as to pass between the Shetland and the Faroe 

 Islands ; so that the whole western coast of the British Islands, having a 

 range of more than eleven degrees of Latitude, lies between the July Iso- 

 therms of 60° and 55°, and the January Isotherms of 50° and 45°. 



152. This northward extension of a Climate so little more severe than 

 that of the South of England, bespeaks some very effective ameliorating 

 agency ; and the question now arises whether this agency is solely that of 

 Wind, as maintained by Mr. Findlay and Dr. Hayes, or is in part exerted 

 by Water. It is argued by Dr. Hayes that the temperature of the Sea 

 follows, and is therefore subject to that of the Air, instead of governing it. 

 Thus, he says, "We have seen and examined the Weather-register kept on 

 " board the Light-ship off Sandy Hook. It shows that the temperature of 



* See Rennell on Currents, pp. 276-2S3. 



