Scientific Intelligence — Geology. 407 



this space is filled with a sort of white, and not very hard clay, which, 

 taking the same direction, forms intermediate beds of a slaty texture. 

 These beds of granite and clay are very little above the level of the 

 sea." 



All this is erroneous. Not a vestige of granite occurs in the country 

 around Tangier. I visited that country in 1814, and passed along the 

 coast from the east of Tangier towards Cape Spartel, where I observed 

 no other rock than sandstone, and a crumbling clay-slate, or rather shale. 

 In my journal is the following note : — 



" Observe that the rocks under the walls of the town consist of alter- 

 nate strata of a yellowish-brown sandstone, of a fine grain, and a crumb- 

 ling bluish slaty clay. The beds of the former are about a foot and a 

 half thick, the latter generally three or four feet. This alternation is 

 continued under the town, and forms the rock on which the castle 

 stands." 



I traced it in various other places on both sides of Tangier ; and Cape 

 Spartel seems to consist of this sandstone. The other indications of 

 granite, mentioned by Ali Bey, between Tangier and Tetuan, I believe 

 to be erroneous ; for the whole of that part of Morocco appears to be 

 exceedingly like, in geological structure, to the opposite coasts of Spain, 

 which, westward of Tarifa, are composed of sandstone. In Barbary, 

 these rocks seldom attain an elevation of above 30 or 40 feet along the 

 coast, until it rises rather abruptly into the rugged and lofty limestone 

 mountains, opposite to Gibraltar, named Apes' Hill by the English, 

 the Mom Ahyla of antiquity — the geological characters of which seem 

 identical with the limestone of Gibraltar, and the eastern Sierras of 

 Andalusia.~T. S. T. 



13. Erupticn of Vemvius of 1843. — M. Rozet reported to the Geolo- 

 gical Society of France, at one of its last meetings, some circumstances re- 

 lative to an eruption of Vesuvius, which he witnessed in September 1843, 

 and which he had leisure to examine in all its details. His report men- 

 tions many facts of a certain degree of importance in explaining volcanic 

 phenomena in general. 



About the middle of July 1843, the holes of the crater of Vesuvius 

 were all stopped, small columns of smoke issued here and there by 

 small fissures, and there was a large prominence near the nortliern 

 edge of the bottom, on which it was easy to walk, although the smoke 

 issued by numerous crevices. On the 30th September, an immense 

 quantity of fumaroles, much more considerable than those of the 

 Solftitara, arose on all the edges of the crater, the interior walls, and 

 even as far as the summit of Palo. These fumaroles issued by fissures 

 and holes, some of which were covered with a pale yellow crust of mu- 

 riate of iron, others surrounded with a white efflorescence of nearly pure 

 marine salt. The smoke was composed of steam, with a small quantity 

 of hydrochloric acid, easily known by its pungent odour, but tliere was 

 so little of it, that the observer could remain in the midst of the smoke 

 for upwards of five minutes, without being put to much inconvenien ce 

 No trace either of sulphur or of sulphureous odour was perceptible. The 

 bottom of the crater was covered with fluid lava, whose black and ex- 

 tremely irregular surface presented numerous fissures, in which the red 

 matter, in a state of fusion, was perceptible. This surface was smoking. 



