THE GEOLOGY OF GIBRALTAE, 533 



of the Queen of Spam's Chair and that neighbourhood. There can 

 be little question that these sandstones are continued out from 

 Spain into the Mediterranean to the east of Gibraltar. It is quite 

 possible, therefore, that the sands of Catalan may have been drifted 

 into their present position by the winds at a time when a low-lying 

 country with an exposed sandy beach existed to the east and north- 

 east of the promontory. On the other hand the sands of Catalan 

 so closely resemble the hardened sands (calcareous sandstone) of 

 Monkey's Cave, &c, as to render it quite probable that they may 

 have had a similar origin. They may merely indicate, as Mr. Maw 

 has suggested, the presence of marine deposits which have been top- 

 dressed, as it were, and obscured by the subsequent action of wind 

 and weather. Were they to become indurated and buried under- 

 neath agglomerate they would present precisely the same appear- 

 ance as the calcareous sandstones of Monkey's- Cave Eoad and that 

 neighbourhood. Be that as it may, however, there can be no ques- 

 tion that the present slope is of comparatively recent origin, and 

 that the sands overlie massive agglomerate which is seen cropping 

 out all along the sea- coast. 



It was probably during the last considerable elevation of the pro- 

 montory that the later limestone-agglomerates were formed. The 

 winters were considerably more severe then than now, so that frost 

 broke up the limestone on the ridges and exposed declivities, and 

 showered debris and blocks in great abundance upon the sand-slopes 

 at Monkey's-Cave Road and upon the raised beaches all round the 

 Rock. 



Then ensued the final movement of depression, which resulted in 

 the present outline of the Spanish coast. It is quite possible, how- 

 ever, that this movement may have carried the land down to a lower 

 level than the present, and that the present position of the Rock 

 may be due to a subsequent upheaval of no great amount, the raised 

 flat that connects the Rock with Spain being perhaps the indication 

 of this latest movement. But there is nothing in the evidence that 

 would seem to make such a supposition necessary. All the facts 

 appear to meet with a simple explanation without it. "We have 

 therefore the following stages represented by the Posttertiary depo- 

 sits at Gibraltar : — 



1. Great imfossiliferous limestone- agglomerate of Buena Vista, Sfc. 

 — Land of greater extent than now ; winters very cold ; Gibraltar 

 apparently not tenanted by the Quaternary Mammalia. 



2. Caves and fissures iviih bone-breccia. — Land of greater extent 

 than now ; Europe and Africa united ; climate genial ; immigration 

 of the African Mammalia. 



3. Platforms or terraces of marine erosion (in part), calcareous 

 sands, fyc. — Depression of the land to the extent of 700 feet 

 below present level ; movement interrupted by pauses of longer or 

 shorter duration ; climate apparently much the same as now. 



4. Platforms of marine erosion (in part); Alameda Sands; for- 

 mation of sand-slopes on east coast, as at Monkey's Gave; mamma- 

 lian remains under beach-obscuring or later limestone-agglomerate 



