]1(3 THE BEDS OF ALUM. 



the island, La Asuncion, the port of Pampatar, and the vil- 

 lages of Pueblo de la Mar, Pueblo del Norte, and San Juan, 

 belong to the second and most easterly of these groups. 

 The western group, the Macanao, is almost entirely unin- 

 habited. The isthmus that divides these large masses of 

 mica-slate was scarcely visible ; its form appeared changed 

 by the effect of the mirage, and we recognized the inter- 

 mediate part through which runs the Laguna Grande, only 

 by two small hills of a sugarloaf form, in the meridian of 

 the Punta de Piedras. Nearer we look down on the small 

 desert archipelago of the four Morros del Tunal, the Ca- 

 ribbee, and the Lobos Islands. 



After much vain search we at length found, before we 

 descended to the northern coast of the peninsula of Araya, 

 in a ravine of very difficult access (Aroyo del Robalo,) the 

 mineral which had been shown to us at Cumana. The 

 mica-slate changed suddenly into carburetted and shining 

 clay-slate. It was an ampelite ; and the waters (for there 

 are small springs in those parts, and some have recently 

 been discovered near the village of Maniquarez) were im- 

 pregnated with yellow oxide of iron, and had a styptic taste. 

 We found the sides of the neighbouring rocks lined with 

 capillary sulphate of alumina in effervescence ; and real 

 beds, two inches thick, full of native alum, extending as 

 far as the eye could reach in the clay slate. The alum is 

 greyish white, somewhat dull on the surface, and of an 

 almost glassy lustre internally. Its fracture is not fibrous, 

 but imperfectly conchoidal. It is slightly translucent when 

 its fragments are thin ; and has a sweetish and astringent 

 taste, without any bitter mixture. "When on the spot, I 

 proposed to myself the question whether this alum, so pure, 

 and filling beds in the clay-slate with out leaving the smallest 

 void, be of a formation contemporary with the rock, or 

 whether it be of a recent, and in some sort secondary, 

 origin, like the muriate of soda, found sometimes in small 

 veins, where strongly concentrated springs traverse beds of 

 gypsum or clay. In these parts nothing seems to indicate 

 a process of formation likely to be renewed in our days. 

 The slaty rock exhibits no open cleft ; and none is found 

 parallel with the direction of the slates. It may also be 

 inquired, whether this aluminous slate be a transition- 



