SMITH ON GIBRALTAR. 47 



sands on the eastern beach. In mineral structure they are precisely 

 the same as those forming at the present day, except that they are 

 hardened into stone by the percolation of calcareous water, and 

 tinged of a reddish colour by the oxide of iron : the separate beds 

 at this particular point are but a fraction of an inch in thickness, 

 but the mass composed of them is nearly 100 feet thick. 



In the same diagram (c) represents beds formed during the pre- 

 ceding period, and these must have been horizontal, as their slope 

 inwards is exactly the amount of the third upheaval. At (d) are other 

 beds formed subsequently to the last upheaval, but when the sea- 

 level was diiFerent : at this locality they form the floor of an ancient 

 sea-worn cave, and contain marine remains. The only species 

 I have been able to make out, the Patella ferruginea, is still to be 

 found recent in the Mediterranean. This last bed I ascertained by 

 barometrical measurement to be nearly 600 feet above the present 

 sea-level. The rough ground on the left represents an extensive 

 landslip, of great antiquity. 



Above this series we come to Martin's Cave ; the floor of it slopes 

 inwards 11°; it is evidently sea-worn, and must have been formed 

 during the preceding period, or that between the second and third 

 upheavals, when it must have sloped outwards 8°, an angle corre- 

 sponding with the present shore, which varies from 8° to 4°. To 

 this period also belong beds of modern sandstone, which are about 

 100 feet higher, or 700 feet above the present sea-level, and which 

 also dip inwards 11°; these last contain marine shells, apparently 

 recent; they occur near the mouth of two sea-worn caves, which 

 however belong to the subsequent epoch, as their floors are hori- 

 zontal. 



Still further to the south other disturbances must have taken 

 place ; but we want the evidence furnished by inclined modern de- 

 posits to ascertain their number and amount. I am inclined to 

 think that one or more upheavals raised up the beds till they became 

 vertical, and then overset them, because we find the beds at the 

 south end of the elevated part of the rock nearly vertical, whilst 

 further to the south they dip in an opposite direction, or to the 

 east ; we have evidence of at least one upheaval subsequent to the 

 last-mentioned. Immediately under that part of the rock where 

 the beds are vertical, there is a sea-worn cave (Flint's) elevated about 

 fifty feet above the sea, with beds of sandstone below it dipping 

 inwards 11°; this indicates that the movement has been in the same 

 direction as those which preceded it, that is, giving the beds a dip 

 to the westward : thus, by a series of consecutive upheavals, the 

 beds have been raised from their original horizontality till they be- 

 came vertical ; beyond this they dip in an opposite direction ; but 

 whether they have been thrown down from the vertical, or raised up 

 from the horizontal position, is a point concerning which I have no 

 evidence to offer. The inclination of the beds of shale on the west 

 side, and the precipice or cliff* already described, were perhaps 

 caused by or connected with the upheavals, of which we have such 

 distinct traces on the eastern side. But this part of the rock is so 



