628 



Dr. W. B. Carpenter on the [June 13, 



earth when its impelling force is exhausted, but may still roll down hill by 

 the force of gravity, which is a new power applied to it, so may Gulf-stream 

 water, and any thing which it floats, be drifted onwards by the action of the 

 Wind, after the propulsive force of the Gulf-stream has died out. 



150. If, then, there be no other Mechanical evidence of the extension of 

 the Gulf-stream proper to Western Europe, than that which is afforded by 

 " Rennell's Current," we have next to inquire what evidence can be adduced 

 of its influence on the Temperature of the Eastern side of the Atlantic. — - 

 This question can be best answered by an examination of the course of the 

 Isothermal lines to the eastward of the Meridian of 30°. For their passage 

 across that meridian between the parallels of 34° and 50° at more regular in- 

 tervals than are seen between them elsewhere, indicates that their position is 

 there comparatively little affected by disturbing causes, either of elevation 

 or depression • and further, the close relation which we there observe between 

 the Winter Isotherms and the Summer Isotherms of 10° higher, indicates 

 that on this meridian the seasonal movement takes place rather in accordance 

 with general Climatic changes than under any special influences. For the 

 Summer Isotherms of 75°, 70°, 65°, and 60° are here nearly equidistant, 

 crossing the Meridian in the parallels of 34°, 41°, 46°, and 50 o, 5 re- 

 spectively ; while the Winter Isotherms of 65°, 60°, 55°, and 50° seve- 

 rally cross it at a distance of scarcely a degree from the preceding. Now 

 whilst, as we have seen(§ 147), the summer Isotherm of 70° and the winter 

 Isotherm of 60° turn southwards to the east of 30° W., the summer 

 Isotherm of 65° and the winter Isotherm of 55° keep their course nearly 

 due eastwards into the Bay of Biscay ; while the summer Isotherm of 60° 

 and the winter Isotherm of 50° in like manner keep an easterly course — a 

 little tending to the north — towards the South of Ireland. There seems 

 no reason whatever for believing that the ordinary temperature of the 

 southern part of the Bay of Biscay is at all higher than the normal of the 

 Latitude. Its winter temperature corresponds very closely with that of 

 the Mediterranean at Toulon, which lies under the same parallel ; while 

 its summer temperature is much lower than that of the centre of Europe. 

 We may, therefore, regard it as ordinarily out of the influence of the Gulf- 

 stream ; though a band of water possessing a temperature above that of 

 the Ocean generally, is sometimes to be met with in a line which may be 

 regarded as that of the Gulf-stream produced. Thus General Sabine, 

 when proceeding, in January 1822, from Plymouth to Madeira, found the 

 thermometer rise in crossing the Bay of Biscay from 49° in Lat. 47^° 

 to 55°' 7 in Lat. 44^°; an increase of 6°'7 being thus shown between one 

 day and the next, although the difference of Latitude alone would account 

 for no more than 2J°. Further south the temperature was found as much 

 below the normal as it here was above it. So again, Dr. Franklin, in his voyage, 

 in November 1776, between the United States and France, found the tem- 

 perature along the produced line of the Gulf-stream much higher than has 

 subsequently proved to be usual ; the thermometer standing at 62° in Long. 



