﻿548 Mr. E. P. Culverwell on the Inadequacy of the 



certainly the effect was not to lower their midwinter tempe- 

 rature to those of 44°'20, 54°, 63°*5, 74°, and 84°*5, at the 

 present time. 



Next as to the transference of heat. Consider the latitudes 

 from Cornwall to the Shetland Isles, i. e: 50° to 60°. In all 

 probability the daily winter transference of equatorial heat 

 to latitude 50° in the period of great eccentricity was greater 

 than that to latitude 54° at present. For there is no doubt 

 that the greater proportion of the transference is due to 

 ocean currents. Now the experiments of the Prince of 

 Monaco on the rate of motion of the Gulf Stream show that 

 between the Azores and Ireland, and between Ireland and 

 Norway, it is about 3*9 miles per day, or say 10 degrees in 

 the half year. Hence the winter heating of the British Isles 

 by means of the Gulf Stream must depend very largely on 

 the daily summer heat at a point about 10 degrees off on the 

 path of the Gulf Stream, and this ivas much greater during 

 the period of greatest eccentricity than now. For it is easy to 

 see by an examination of fig. 2 that during the 166 days of 

 that short summer, latitude 50° received more heat than is 

 now received in an equal time by any latitude, even in the 

 tropics, while 60° received as much as 52° now receives, 70° 

 as much as 59°, and 80° as much as 66° now receives. Thus 

 when we remember how important a factor in winter tempe- 

 rature the heat transferred by ocean currents is, it might be 

 plausibly maintained that the winter temperatures of the 

 higher latitudes were probably higher in the supposed Glacial 

 epoch than they are at present. But as the data are in- 

 sufficient for obtaining a quantitative result by such arguments, 

 it is better to be content with the extreme temperature limit, as 

 fixed by the third method. This is obtained as follows : — 



As we go northwards from latitude 50° to latitude 70° 

 along the meridian of Greenwich we get a fall of 15° Fahr. 

 in the midwinter temperature. Hence in that longitude 

 the midwinter temperatures of latitudes 54°, 63°' 5, and 74° 

 are about 3° Fahr. lower than those of 50°, 60°, and 70°. 

 Hence the fall of temperature in the epoch of greatest eccen- 

 tricity cannot have been as much as 3° Fahr. in Great Britain, 

 so far as the direct effect of sun-heat is concerned. 



In mid- America and mid-Asia the change is somewhat 

 greater. Taking the mean as we go northward from lat. 50° 

 to lat. 70° along the meridians 90° W. long, and 90° E. long., 

 we find that the midwinter temperature falls by 1 J° Fahr. for 

 each degree of latitude passed over to the northward. This 

 would give a lowering of midwinter temperature of about 

 5° Fahr. for the 4 degrees of latitude by which the iso- 

 thermals are shifted in the epoch of greatest eccentricity. 



