534 A. C. EAMSAY AND J. GEIEIE ON 



(perhaps cave-deposits in part). — Eeelevation ; land of greater extent 

 than now (Africa and Europe perhaps reunited) ; climate probably 

 genial. 



5. Later limestone-agglomerates resting upon and obscuring erosion- 

 terraces and sand-slopes, Sfc. — Geographical conditions probably 

 same as during part of 4 ; winter considerably more severe than 

 now. 



6. The present. — Characterized by the absence of the action of 

 frost. 



Concluding Remakes. 



Cause of the cold conditions that gave rise to the formation of the great 

 Limestone-agglomerates. 



At first sight there would seem to be little difficulty in accounting 

 for the cold conditions of climate that obtained at the Rock during 

 the accumulation of the great agglomerates. Knowing that Europe 

 and Africa must have been united in Quaternary times so as to allow 

 of the immigration into our Continent of the African Mammalia, one 

 is apt to conclude that when this union existed the Rock of Gibral- 

 tar might have reared its head to such an extent as to bring it under 

 the influence of sharp frosts. "We do not know, however, whether 

 the two continents were connected at the time the great agglome- 

 rates in question were accumulated. All the evidence goes to show 

 that the Pleistocene Mammalia did not make their appearance in 

 Gibraltar until long after the formation of the older agglomerates of 

 Buena Yista. Of course it is quite possible, and even probable, that 

 they entered Europe before that; but, if so, there is no trace of that 

 early immigration to be detected in the superficial deposits of Gibral- 

 tar, the evidence must be sought for elsewhere. 



If, therefore, we attribute the formation of the older unfossiliferous 

 agglomerates to a former greater elevation of the Rock, we of course 

 indulge in a mere guess, since it is quite impossible to show that 

 the Rock was then much more than one or two hundred feet higher 

 than it is now. Besides, the height to which it would be necessary 

 to elevate the Rock to bring about the required climatic conditions 

 is such as to make it extremely improbable that an elevation of the 

 land was the cause of the cold. 



A comparison of the present monthly mean temperatures of Gi- 

 braltar with those that would obtain were the height of the Rock 

 to be increased by 1000 feet or so, will show that Europe and Africa 

 might have been connected across the Straits of Gibraltar so as to 

 allow of the immigration of the African Mammalia without Gibral- 

 tar having been subjected to severe winters. To the kindness of 

 Mr. Buchan, of the Scottish Meteorological Society, we are indebted 

 for the following Table, which shows the mean and minimum tem- 

 peratures, on the average of ten years (1853-59 and 1864-68), at a 

 height of about 48 feet. 



