172 



Thus by means of the refraction, and notwithstanding the 

 curve of the Earth, which at the distance P Q would conceal 

 a mountain of 370 toises, we might sometimes see a mountain 

 situate on the coast only 202 toises high $ but as the refrac- 

 tions are uncertain, and may even be negative, it would be 

 imprudent to affirm any thing for such great distances, for 

 which we have no observation. 



Results of the determinations of height. 



toises. 



Town of JLaguna - - 360 



— —— Orotava - - 163 



Pino del Dornajito - - 533 



Estancia de los Ingleses " - - 1552 



Cavern of Ice - - 1732 



Foot of the Piton - - - - 1825 



Summit of the Peak of Teneriffe - - 1909 



I have given in the third chapter* the result of the ob- 

 servations of longitude which I made at Santa Cruz. The 

 following are the data taken from Mr. de Borda's manu- 

 script, and which will serve to complete what has been laid 

 down in the Collection of my astronomical observations (t. i, 

 p. xxxvii and 28) . Don Joseph Varela observed, the 30th of 

 August, at the port of Gomera, the immersion of Jupiter's 

 third satellite, at 15 h 40' 8". Tofino saw, at Cadiz, this 

 same immersion, at 16 h 23' 28". Difference of the meridians 

 43' 20" j the port of la Gomera ? being situate, according to 

 the operations of Borda 0 h 3? 28" to the east of Santa Cruz, 

 we 'find for this latter place 0 h 39' 52". The 12th of Oc- 

 tober, Varela observed the immersion of the third satellite at 



* Vol. i, p. 117. 



