300 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



cially alluded to as exhibiting much grandeur and great picturesque 

 beauty. Northward of this mountain clay slate is described as 

 being present, and near it, by the banks of the Carimani, black 

 quartz, while in the basin of the river Cuyuni large blocks of 

 coarse conglomerate were seen, although near the junction of that 

 river with the Mazaruni the rocks were basaltic. The rocks at the 

 great falls of Ematupa are said to consist of ^granite and dark in- 

 durated clay slate. 



The author next directs attention to various rocks of grotesque 

 form, found in the granitic district of Guiana ; some of these, 

 called the ' pyramids,' being of granite and other porphyritic rock, 

 and forming very striking objects in the landscape. 



In conclusion, the author states that the geological features of 

 Guiana in some districts render it most probable that gold is pre- 

 sent, and that he found specimens in the river sand of the Takutu, 

 which, judging from the tests he was able to employ, he had no 

 doubt were fragments of this precious metal. These specimens, 

 however, with many others, were lost in the course of his journey ; 

 but Fray Jose, the catholic missionary, showed him a piece of 

 massive gold partly embedded in quartz, which had been found on 

 the banks of the Rio Branco where the Takutu enters that river, s 



The presence of Itakolumite, of mica slate, and of what in Brazil 

 is called the Diamond matrix, proves the existence of a structure 

 in the Savannah regions of Guiana similar to that of the Serra 

 do Espinhaco in the province of Minas Geraes in Brazil. 



2. A Letter to Dr. Buckland on the subject of Glacier Marks 

 in South Wales. By W. C. Trevelyan, Esq. 



The object of this letter was to direct attention to certain polished 

 and scratched surfaces in the valley of the Conway on the ascent 

 of Moel Siabod and in other places near Snowdon. The author 

 considered that these and other markings he had observed were in- 

 dications of the former presence of glaciers in these localities. 



December 18, 1844. 



The following gentlemen were elected Fellows of this Society : 

 — Robert Chambers, Esq., of Edinburgh ; James Simpson, Esq., 

 of Chelsea ; William Lewellyn, Esq. of Pont-y-Pool ; and James 

 Bandinel, Esq. of Westminster. 



The following communication was read : — 



On the Pipes or Sand-galls in the Chalk and Chalk-rubble of 

 Norfolk. By Joshua Trimmer, Esq., F. G. S. 



In a paper read before the Society in the Session of 1842-3, and 



