( 65 ) 



On the Lacustrine Basins of Baza and Alhama, in the Pro^ 

 vince of Granada in Spain. By Colonel Silvertop, 

 M. G. S. Ti. Communicated by the Author. — (Cmichided 

 from former volume, p. 349- J With a Plate. 



BASIN OF ALHAMA. 



Ihe geographical position of this basin was alluded to in 

 general terms at the commencement of my last communication. 

 It occupies a large circular area, at the distance of about fifty 

 miles to the south-west of that near Baza, on the northern side 

 of the primitive and transition chain of mountains which border 

 the Mediterranean ; and it is chiefly surrounded by primary 

 rocks towards the south and east, and by ridges of secondary 

 limestone towards the north and west *. In the latter, close to 

 a town called Loja, at the western extremity of the basin, there 

 is a chasm through which the river Genii f , rising in the Sierra 

 Nevada to the east of Granada, is enabled to escape, and to pur- 

 sue its course to the Guadalquivir ; but beyond this chasm the 

 secondary limestone is continued, and, circling round towards the 

 east north-east, forms the boundary of the basin towards the 

 north. A considerable portion of this ridge is known by the 

 name of Sierra de Cogollos, and the distance from it to the op- 

 posite ridge near Alhama, may be taken as the greatest length 

 of the basin ; that from a village called Escuzar, on its eastern 

 side, to the town of Loja, as its greatest breadth ; the former be- 

 ing equal to about thirty-six, the latter to about thirty miles. 

 One insulated group of transition limestone, named La Sierra de 



• In the southern boundary of this basin, a junction between the primary 

 and secondary rocks occurs between a pass called El Puerto de Zafarraya and 

 the western flank of a high mountain, well known to botanists, and called La 

 Sierra de Tejeda : in the northern boundary a similar junction takes place, 

 near a village called Huetor de Santillana, about four miles from Granada, 

 on the road to Guadiz. At neither of these points, however, is there any 

 interruption of continuity in the bounding ridges, the secondary limestone in 

 both instances appearing to come in contact with, and to rest upon, primary 

 rocks of a similar composition or basis; that near Huetor being agranular, 

 that of Tejeda a lamellar limestone, and both highly crystalline. 



f The classic vale, the Vega de Granada, watered by the Genii, has been 

 immortalized in song and in prose, as the theatre of many a chivalrous deed 

 in the dden times. 



OCTOBBR— DECEMBER 1830. E 



