145 



DETERMINATION OF THE HEIGHTS OF SEVERAL 

 POINTS IN THE ISLAND OF TENERIFFE. 



1 shall, in this dissertation, discuss the trigonometrical 

 and barometrical measurements, made within the last cen- 

 tury, by various travellers, who have visited the island of 

 Teneriffe ; and at the same time give an historical sketch of 

 the attempts,, which have been made to ascertain the height 

 of the Peak of Teyde, and of the most remarkable points on 

 the road leading to the top of this volcano. It is highly in- 

 teresting, not to the science of geology alone, to know with 

 precision the absolute height of this mountain j this know- 

 ledge is also necessary to perfect the charts of the Canary 

 Islands, because Messrs. de Borda and Varela, at the time of 

 the voyage of the frigate la Boussole, made use of the verti- 

 cal angles of the Peak and the azimuths, to ascertain the re- 

 lative distances of Teneriffe, Gomera, and Palma. 



Although as early as the year 1648, the experiments of 

 Pascal and Perrier had proved, that the barometer might be 

 successfully applied to measures of height, it is however only 

 since the beginning of the 18th century that we have accu- 

 rate ideas of the elevation of a few mountains. Riccoli still 

 gave ten Italian miles, and Nichols fifteen leagues of height 

 to the Peak of Teyde*. Eden did not attempt to measure 

 the height, though he reached the summit of the volcano in 

 1715. His voyage f however, the earliest that was publish- 

 ed, fixed the attention of the geographers and natural phi- 

 sophers of Europe ; and the first attempt at measuring the 

 height of the Peak was made by P. Feuille'e % in 1724. This 



* Zach, Journ. Astron., 1800, t. i, p. 396. Vieyra, No- 

 ticias tlistoricas, t. i, p. 234. 



f Phil. Trans., vol. xxvii, p. 317. 



t Manuscript Journal ofPere Feuillee. 



