536 A. C. RAMSAY AND J, GEIKIE ON 



the refrigeration which produced these accumulations could have 

 been brought about by the former greater elevation of the land. 



But it may be said that an elevation of as much as 7000 feet 

 would not be necessary if, as some geologists believe, the Sahara 

 happened to be submerged during the Pleistocene period. But, sup- 

 posing such submergence to have actually taken place in Pleistocene 

 times, what evidence is there to show that the drowning of the 

 Sahara coincided in point of time with the formation of the unfos- 

 siliferous agglomerates of Gibraltar, or, for that matter, with the 

 appearance of land-passages across the Mediterranean? It is certain 

 that a movement of depression occurred during the formation of the 

 Posttertiary deposits of Gibraltar, by which the Bock was carried 

 down 700 feet below its present level, the actual amount of depres- 

 sion being probably not less than 2200 feet, for the two continents 

 were certainly connected in times immediately preceding that de- 

 pression. Again, a subsequent movement of elevation lifted the 

 Rock considerably above its present level, and may even have re- 

 stored the connexion of the continents ; and it is certainly not un- 

 reasonable to infer that these movements of depression and elevation 

 may have extended southward, so as to influence the level of the 

 Sahara. When a land-passage existed between Spain and Barbary, 

 the region of the Sahara may likewise have been relatively higher 

 than now ; and, again, when the shell-beds of Gibraltar were being 

 formed, the sea may also have covered all the low-lying tracts of the 

 Sahara. But, as we have seen, the raised beaches of the Bock con- 

 tain shells of living Mediterranean species, so that climatic conditions 

 during the depression were certainly not colder than at present. 



To what extent the Sahara may have been depressed in Pleisto- 

 cene times we have no certain evidence to show. From the pre- 

 sence of certain deposits at a height of 2000 feet south of the Tell 

 plateau, as described by Mr. Maw, and supposed by him to be marine, 

 Mr. Dawkins has inferred that the Pleistocene submergence may 

 have reached to that extent at least. Unfortunately, however, the 

 deposits in question appear to be unfossiliferous, and we cannot be 

 sure, therefore, whether they are even marine. And if they really 

 be marine they are more likely to be of Newer Pliocene than Pleis- 

 tocene age ; for while we have no evidence in the Mediterranean 

 area of any great Pleistocene depression, we have the most abundant 

 proof of a very great submergence in Newer Pliocene times. The 

 chances, therefore, are much in favour of any high-level marine de- 

 posits of apparently recent formation that may be found bordering 

 the Sahara being of Newer Pliocene age. Be that, however, as it 

 may, there is nothing in the evidence that would lead us to suppose 

 that a great Pleistocene depression of the Sahara and Northern 

 Africa coincided in time with a considerable elevation of the Medi- 

 terranean area. On the contrary, it seems more reasonable to infer 

 that, if the Sahara was really under water in Pleistocene times, this 

 submergence was probably contemporaneous with the greatest de- 

 pression ever experienced at Gibraltar. For the sake of argument, 

 however, let it be admitted that a Sahara sea was actually contem- 



