70 CANARY ISLANDS. 



By means of this, I calculated a second « c of 1430*06 

 toises, and afterwards a third a p of 9953-4 toises, which 

 was the first grand base required. The point c was in 

 Mr. Cologan's garden in La Villa de la Orotava, near the 

 great dragon-tree spoken of in a former letter ; and the 

 point p was the summit of the Peak. The base a b was 

 measured by Mr. Hurst of London, and myself, on three 

 occasions, each of the measurements terminating with 

 nearly the same results. The following were the angles 

 of the two triangles taken with minute attention. 



Triangle ah c. Triangle a cp, . 



Angle o6c = 86° 00' Angle a cp = 119° 58' 



" a c6 = 4 00 ^' ap c = 7 13 



" 6«c = 90 00 " cap — 52 49 



At the point a, the Peak subtended an angle of 10° 35', 

 by means of which, I found that its summit is elevated 

 1859-73 toises above the point a. 



My next object was to determine the height of the point 

 a above the ocean. In order to do this, I employed the 

 same basis a 6 of 100 toises as in the preceding triangle, 

 from which I calculated another a o of 1339-46 toises, 

 which was the second grand base required. The point o 

 was a vessel riding at anchor in the quarantine of this port. 

 The follov*'ing were the angles of the triangle a b o, taken 

 in the same manner as those of the other triangles. 



Angle abo = 137° 58' 

 " aoh — 2 55 

 " hao =z 39 07 



The angle of depression from the point a to the point o, 

 was 19° 49', and of course, the angle of elevation from the 

 point to the point a, was the same. From these data, I 

 ascertained that the point a was elevated 48.26 toises 

 above the ocean. The height of the eye above the point 

 «, in taking the angles of elevation and depression, was 

 1-5 toises ; and the state of the atmosphere at the time that 

 the angles were taken, was perfectly serene, on account of 

 which, I only deducted, for the effect of refraction, 2-34 

 toises. Hence we may infer from the foregoing operations, 



