Dr. Ricketts — On the Cause of the Glacial Period. 575 



petual snow existed as far south as the latitude of New York, and 

 the greater part of Europe was covered with it ; the wind passing 

 over a land surface of such extent and having a glacial temperature, 

 would have had almost the whole of its water condensed out 

 of it long before reaching the Arctic Circle. " The wet would be 

 squeezed out by the cold, as water is wrung from a sponge." 1 Even 

 when the winds have to pass over land, the mean temperature of 

 which is considerably above the freezing-point, the air parts with so 

 much of its moisture that at no time, since the Mammoth and woolly- 

 haired Ehinoceros roamed over the plains of Siberia, has there been 

 in Northern Asia so great an accumulation of snow as to form 

 glaciers ; otherwise the remains of these animals, found in the banks 

 of the Lena, would have been swept by them into the Arctic Sea ; 

 yet during all that time the soil, in which they have been imbedded, 

 has continued so persistently frozen that their remains have been 

 preserved with the soft parts undecomposed. 



It does not at all follow that, with diminution of temperature in 

 the Arctic regions, there should also have been at the same time 

 reduction of the winter temperature of the British Isles. The 

 present temperate and equable climate of Britain is dependent on 

 the warmth of the waters which, derived partly from those of the 

 Gulf Stream and at a lower temperature from those of the 

 Temperate Zone, are carried as a set or current towards the Polar 

 regions ; and, being many degrees higher than would otherwise be 

 the mean annual temperature of the British seas-, modify also the 

 temperature of the air passing over them. 



Dr. Carpenter has, as I believe, demonstrated that what I will 

 call the North Polar Current (termed in Johnston's Physical Atlas, 

 "North-East Branch of the Gulf Stream") is dependent on the 

 effects which diminution of temperature in the Polar regions has 

 in causing the displacement by sinking of the surface water of the 

 Arctic Sea, the density of which has been increased by the tempera- 

 ture being diminished, and the necessary influx of lighter water, 

 that is, the comparatively warm water derived from the Gulf Stream 

 and the Temperate Zone, to replace the colder which has subsided. 



The North Polar Current thus produced, and consisting of water 

 very much warmer than the surface temperature of the North 

 Atlantic would be, if this current did not exist, supplies heat and 

 moisture to the atmospheric currents passing over it ; so that partly 

 on this account, and partly from the inability of heat to radiate so 

 readily from the surface of the land in consequence of the frequent 

 cloudiness of the sky, the winter temperature of Britain is con- 

 siderably milder than it would be under different conditions ; whilst 

 in summer it is often modified by the difficulty with which the sun's 

 rays can penetrate when, from the same cause, there is an excess 

 of cloud or vapour in the atmosphere. If the peninsula of Florida 

 did not exist, the winter temperature of Britain would be still 

 milder, as, in consequence of it, the Gulf Stream has to traverse 

 a distance of several hundred miles more than would be the case 

 otherwise. 



1 J. Campbell, F.G.S. " Frost and Fire." 



