244 TKANSACTIONS AND PROCEEDINGS OF THE [Sess. lxvi. 



direction, as the snow spread still farther outward. Thus, 

 with extreme slowness, and without any violent catastrophe, 

 the temperate Germanic flora spread to more congenial 

 stations ; the Scandinavian Alpine flora followed, and the 

 Arctic flora brought up the rear, each extension southward 

 probably keeping pace with the slow advance of the nivosal 

 conditions. 



There is evidence to show that the Arctic fauna kept 

 pace with its corresponding flora, and that, in the end, both 

 had extended their range to countries hundreds of miles away 

 from their normal stations. 



It is not difficult to understand how other changes that 

 affected plant life were brought about. The piling up 

 of extensive and thick mantles of ice over all the ground 

 from Scandinavia across Britain to the south of Ireland, 

 gave rise to exceptional meteorological conditions, perhaps 

 affecting the isobars very materially, and certainly acting 

 in another way which produced important effects upon 

 plant life. I have held for so many years that the chief 

 cause of the nivosal conditions that prevailed during the 

 Age of Snow were the existence of the " Gulf Stream " 

 close to the 100-fathom line west of Britain and Scan- 

 dinavia, at a time when the land stood at a much higher 

 level than it does now. One consequence that must have 

 followed from the southward extension of the ice, was that 

 nearly the whole of the aqueous vapour present in the aerial 

 accompaniment of the " Gulf Stream " was either chilled 

 into fog or congealed into snow close to the western margin 

 of the land. The winds passing over the midland and 

 eastern parts of the country were therefore cold, dry winds, 

 all the moisture that could be got out of them having 

 already been deposited on meeting with the upland area on 

 the west. These dry winds, therefore, must sooner or later 

 have given rise to steppe conditions. That such conditions 

 did exist has clearly been shown by Mr. Keid. We have 

 the remains of many steppe animals entombed in deposits 

 of this age. And if there was a steppe fauna, it appears 

 safe to conclude that there was a steppe flora present as 

 well. 



The chronological order of change over any given area, 

 so far as the flora is concerned, seems, then, to be thus — first. 



