417 



by an uncommon exception in that country, 

 does not dip to the north-west, but to the south- 

 east, which prevents the subterraneous waters 

 from forming 1 springs there. 



We continued to descend from the small 

 ravin of Sanchorquiz to la Cruz de la Guay- 

 ra ; a cross erected on an open spot, six hun- 

 dred and thirty-two toises high, and thence 

 (entering by the customhouse and the quarter 

 of the Pastora) to the city of Caraccas. On the 

 south side of the mountain of Avila, the gneiss 

 presents several geognosticai phenomena worthy 

 of the attention of travellers. It is traversed by 

 veins of quartz, containing canulated and often 

 articulated prisms of rutile titanite of two or 

 three lines in diameter. In the fissures of the 

 quartz we find, on breaking it, very thin crys- 

 tals, which crossing each other form a kind of 

 network. Sometimes * the red schorl occurs 

 only in dendritic crystals of a bright red. The 

 gneiss of the valley of Caraccas is characteriz- 

 ed by the red and green garnets, which it in- 

 cludes, and which disappear when the rock 

 passes into mica-slate. This same phenomenon 

 has been remarked by Mr. Von Buch in Sweden, 

 in Helsingland, while in the temperate parts of 

 Europe garnets are in general contained in the 

 serpentine and mica-slates, not in gneiss. In 



* Especially below the Cross of La Guayra, at 594 toises 

 of absolute elevation. 



VOL. III. 2 E 



