RANGE BASE OR REFUGE AREAS 51 



routes of birds. The northern portions of this area pro- 

 bably differed little, if at all, in their climate from portions 

 of the preceding refuge area within the same parallels 

 of latitude ; the climate of the southern portions we 

 may reasonably infer was not influenced to any great ex- 

 tent by the Glacial Epoch, although mountainous regions 

 have unquestionably suffered some local modification 

 in this respect. Proof of geologically recent change of 

 climate in East Africa was obtained by Mr. J. W. 

 Gregory in his expedition to Mount Kenya. Mounts 

 Kilima Njaro and Elgon, the mountains of Abyssinia 

 and the Cameroons, I believe I am correct in stating, 

 furnish additional proofs of local climatic change, due to 

 more intense glaciation in remote ages. There is also 

 much evidence to suggest that North-east Africa at no 

 geologically remote epoch was much more wooded 

 than is now the case — conditions that would favour the 

 western emigration of arboreal forms (cojtf. Map, p. 95). 

 Of course it must be clearly understood that the 

 climate of these refuge areas, most especially in the 

 first, underwent considerable variation during the course 

 of the Glacial Epoch, which, as we know, was made up 

 of a series of alternate mild and cold periods. Mild 

 climatal conditions were succeeded by eras when the 

 cold was more intense, and these in their turn gave way 

 to warmer ones ; at one time the summers must have 

 been short and hot, the winters long and intensely cold ; 

 at another, longer and colder summers prevailed, and 

 the rigours of winter were less severe, or the seasons 

 were more blended ; whilst yet again the pluvial con- 

 ditions of the warm season were much intensified during 

 certain epochs. Vast plain and valley floods were the 



