IMMENSE PRECIPICE. J 33 



ing left nothing but a few olives and a little bread. The chap. xil. 

 guides were discouraged, and were with difficulty pre- 

 vented from returning;. 



In the midst of the fog the electrometer of Volta, Atmospiicric 

 armed with a smoking match, gave very sensible signs «'ectncity. 

 of atmospheric electricity, varying frequently from 

 positive to negative, and. this, together \\ith the conflict 

 of small currents of air, appeared to indicate a change of 

 weather. It was only two in the afternoon, and they 

 yet entertained some hope of reaching the eastern sum- 

 mit before sunset, and of returning to the hollow 

 separating the two peaks, where they might pass the 

 night. With this view they sent half of their attendants 

 to procure a supply, not of olives but of salt beef. 

 These arrangements were scarcely made when the east 

 wind began to blow violently, and in less than two 

 minutes the clouds disappeared. The obstacles pre- 

 sented by the vegetation gradually diminished as they 

 approached the eastern summit, in order to attain which 

 it was necessary to go close to the great precipice. 

 Hitherto the gneiss had preserved its lamellar struc- Geological 

 ture ; but as they climbed the cone of the Silla they features. 

 found it passing into granite, containmg instead of 

 garnets a few scattered crystals of hornblende. In three 

 quarters of an hour they reached the top of the pyramid, 

 which was covered with grass, and for a few minutes 

 enjoyed all the serenity of the sky. The elevation 

 being 8683 feet, the eye commanded a vast range oi 

 country. The slope, which extends nearly to the sea, 

 had an angle of 53° 2B', though when viewed from the 

 coast it seems perpendicular. Humboldt remarks that 

 a precipice of 6000 or 7000 feet is a phenomenon much 

 rarer than is usually believed, and that a rock of 1600 

 feet of perpendicular height has in vain ])een sought for 

 among the Swiss Alps. That of the Silla is partly 

 covered with vegetation, tufts of befariae and andromedse 

 appearing as if suspended from the rock. 



Seven months had elapsed since they were on the 

 summit of the Peak of Teneriffc, where the apparent 



