162 



had a telescope, and a chronometer, of which I 

 knew the great exactness. In the part where the 

 sun was to appear, the horizon was free from va- 

 pors. We perceived the upper limb at 4h 48' 55" 

 apparent time, and what is very remarkable, the 

 first luminous point of the disk was found im- 

 mediately in contact with the limit of the hori- 

 zon ; consequently we saw the true horizon, that 

 is to say, a part of the sea farther than 43 kagues. 

 It is proved by calculation, that, under the same 

 parallel in the plain, the rising would have be- 

 gum at 5 h 1' 50*4", or 11' 513" later than 

 at the height of the Peak. The difference ob- 

 served was 12' 55", which arose no doubt from 

 the uncertainty of the refraction for a zenith 

 distance, of which observations are wanting*. 



We were surprised at the extreme slowness, 

 with which the lower limb of the sun seemed to 



* In this calculation we bave supposed, that for an appa- 

 rent zenith distance of 91° 54 r , there are 57' 7" of refraction. 

 The rising sun appears sooner at the Peak of Teneriffe than 

 in the plain by the time that it takes to pass through an arc 

 ofl°54 / . The greatness of the arc is augmented only 41' 

 for the summit of Chimborazo. The ancients had such ex- 

 aggerated ideas of the acceleration of the rising of the sun on 

 the top of high mountains, that they admitted, that this lu- 

 minary was visible on Mount Athos three hours sooner than 

 on the coast of the Egean sea (Strabo edit. Almeloven } lib. vii, 

 p. 510) : yet Mount Athos, according to Mr. Delambre, is 

 only 713 toises high. (Choiseul Gouffier, Voy. pitt. de la Grece, 

 t. ii, p. 140.) 



