538 A. C. KAMSAY AND J. GEIKIE ON 



thick cloud of vapour envelops the Rock. Gibraltar lies so near the 

 Atlantic, however, that its general summer temperature is not greater 

 than that of places situated considerably further to the north, as 

 Madrid, Barcelona, Perpignan, Montpellier, &c. ; but in winter the 

 mean temperature of the Rock is some 9° higher than at these places. 

 It is evident, indeed, that the proximity of the Atlantic exercises a 

 predominant influence upon the temperature, giving to Gibraltar a 

 kind of insular climate. 



Now, if the Sahara were submerged, it is certain that the Solano 

 or Levanter would cease to blow, and the temperature in the western 

 basin of the Mediterranean would be reduced in summer, but 

 the change of temperature at Gibraltar would be very small. We 

 have seen that an elevation of the Rock for 1500 feet or so would 

 lower the temperature only 4° or 5°; and even this slight reduction 

 would probably be lessened by the influence of the physical condi- 

 tions that would obtain upon a general elevation of the Mediterra- 

 nean area for 1500 feet or thereabout. "We must remember that 

 such a degree of elevation would convert the Mediterranean into two 

 salt lakes, the eastern one of which would receive the drainage of 

 several great rivers, while the western basin would be supplied by 

 no river larger than the Rhone. In this latter basin, therefore, eva- 

 poration being much greater than the influx of fresh water, the level 

 of the inland sea would be gradually lowered, and the area of land 

 increased, so that in course of time the western lake might be re- 

 duced to very moderate proportions, and this would of course tend 

 to increase the summer temperature along its borders. Thus any 

 lowering of summer temperature that might take place at Gibraltar, 

 owing to the elevation of the land and the influence of the Sahara 

 Sea, would gradually be lessened as the western salt lake continued 

 to contract. 



In winter no dry winds would come from the Sahara, all the 

 southerly winds would be warm but moist; and we may easily be- 

 lieve, therefore, that the glaciers on the south side of the Alps would 

 increase to some extent, so as perhaps to rival in importance the 

 Swiss glaciers of to-day. We can hardly suppose, however, that 

 the winter temperature of Gibraltar would be reduced. There would 

 not be the same powerful radiation as now in the Sahara region ; but 

 the sea spread over that area, retaining its high temperature for a 

 longer period, might be expected to increase the warmth of the 

 Mediterranean area ; for, as Mr. Buchan remarks, the submergence 

 of the Sahara " would bring about a marked diminution of aerial 

 and oceanic currents from the north over and off the north-west of 

 Africa." It is with the winter climate of Gibraltar, however, that 

 we are principally concerned, and not with that of the whole Medi- 

 terranean area. And it seems impossible to doubt that, even under 

 the physical conditions supposed, the winter temperature at the Rock 

 would remain much as it is now. The rainfall would probably be 

 greater, but the proximity of the Atlantic would tend then, as now, 

 to prevent any extreme winter climate. 



From these and other foregoing considerations it seems most rea- 



