152 



not be employed, I measured with the greatest exactness the 

 two angles c d P, and d c P, by means of a reflecting circle ; 

 and 1 found only from 8 to 10 seconds of difference. Hence 

 it follows, that the angle at the Peak, d P c is 9° 25' 20". 

 We And also a c = 3686 2 feet ; a d = 8647 3 feet j c d = 

 9159-5 feet ; c P = 55814*6 feet ; and d P = 54420 9 feet. 

 The vertical angles give the following heights of the Peak, 

 or of the different stations from one another. Altitude of the 

 Peak seen from point d, =z 10423*2 feet ; the same seen from 

 the point c, — 11116 feet ; that of the point d above the point 

 a, = 733*6 feet j the same above the point c — 687*6 feet ; 

 and that of the point c above the point a =. 47*3 feet. 

 From these data, the height of the Peak above the point d 



Feet. 



being - - - - - 10423*2 



if we add the height of the point d above the point a 733*6 

 we have a first height of the Peak above the point a 11156*8 

 In the same manner, that of the Peak above the 



point c being - - - -. 11116*0 

 If we add that of the point c above the point a 47*3 

 we have a second height of the Peak above the 



point a - - - - 11163*2 



** Taking the mean of these two results, we find 1 1160 feet j 

 and on deducting for the effect of the refraction 13*7 feet, 

 we have 11146*3 feet. It now remains to determine the 

 height of the poiijit a above the level of the Ocean. The 

 depression of the horizon of the sea, at a, was 17' 11", and 

 at d, 32' 25". According to these depressions, the point a 

 is raised above the level of the Ocean 283- 6 feet; and on 

 adding this quantity to the height of the Peak * above the 



* Mr. de Borda had found, on his first calculation, 1904 

 toises, assuming nineteen feet for the effect of the refraction. 

 He has not indicated the apparent altitudes ; but we may 

 deduce them from the values of d P and c P. At c the Peak 



