Geological Society. 67 



the St. Lawrence winding its way through a vast extent of level 

 country, while in various parts extensive wooded islands were seen 

 obstructing its course. On descending the south side of the moun- 

 tain, which is closely wooded, the thermometer indicated 89° of 

 Fahrenheit. The exertion caused by ascending and descending was 

 severe ; and owing to the parched state of the ground, and the flaccid 

 vegetables with which it was covered, walking was rendered nearly 

 as difficult as over sea-weeds on a rocky shore." 



At this meeting the election of office-bearers for the ensuing year 

 took place, when Dr. Douglas Maclagan was chosen President ; and 

 Professor Graham, Drs. Lowe, Greville and Seller, Vice-Presidents. 



GEOLOGICAL SOCIETY. 



Nov. 20, 1844. — A paper was read " On the Geology of Gibraltar." 

 By J. Smith, Esq., of Jordan Hill. 



The great rocky masses terminating Europe on the S.W. and 

 Africa on the N.W., and cut through by the Straits of Gibraltar, con- 

 sist of siliceous sandstones, associated with limestone, chert, shale and 

 coal, all apparently of the oolitic formation. The Gibraltar limestone 

 contains casts of Terebratula fimbria and T. concinna, species found in 

 Britain in the lower oolite. The covering of the older rocks consists 

 of soil, river alluvium, post-tertiary marine sands, and local patches 

 of diluvium. Wherever the covering is removed, the surface of the 

 rock beneath is seen to be water- worn. The rock of Gibraltar is 1470 

 feet high. The southern extremity is marked by a triple series of 

 terraces and inland cliffs, formed by the sea at former levels. Its 

 northern terminates in a perpendicular cliff. 7'he elevated part is 

 divided into three distinct eminences, the effects of different local 

 upheavals. The northern of these (the rock gun) does not appear 

 to have undergone any derangement in its stratification since its first 

 upheaval, although it must have been subjected to many elevations 

 and depressions of level. Its older beds (those of the limestone) dip 

 west at an angle of 20°, and those formed since the elevation are 

 horizontal, remaining in their natural position. In this state the 

 whole of the rock must have remained for a lengthened period, until 

 a second upheaval broke it across, leaving the northern portion in its 

 original position, but lifting the whole of the southern 20° more, so 

 that its beds, which formerly dipped 20° west, now dip 40° ; and the 

 fresh deposits, formerly horizontal, 20°. On these deposits, others, 

 formed after the upheaval, rest unconformably. A third upheaval in 

 the same direction, but still further to the south, lifted the rock there 

 about 20° more, leaving the northern and middle hills in their former 

 position, but inclining the southern 60°. Thus we have four distinct 

 epochs ; of the deposits formed during each we have remains, and at 

 Martin's Cave the whole may be seen in juxtaposition. Immediate- 

 ly under O'Hara's tower, the highest peak, the inclination of the 

 beds to the west is nearly 80°, and a short way to the south of it, 

 they are vertical. Under this point there is, at the height of about 



F2 



