482 



ed the whole night in watching three occulta- 

 tions of the satellites of Jupiter. I had previously 

 determined the instant of the observation ; but 

 we missed them all, owing to some error of cal- 

 culation in the Connaissance des Temps. * An 

 evil destiny presided over the occultations of the 

 months of December and January. The appa- 

 rent time had been taken for mean time *. 



I was singularly disappointed by the acci- 

 dent ; and after having observed at the foot of 

 the mountain the intensity of the magnetic 

 forces before sunrise, we set out at five in the 

 morning, accompanied by slaves carrying our 

 instruments. There were eighteen of us, walk- 

 ing one behind another, in a narrow path, traced 

 on a steep acclivity, covered with turf. We 

 endeavoured first to reach a hill, which toward 

 the south-east seems to form a promontory of 

 the Silla. It is connected with the body of the 

 mountain by a narrow dyke, to which the shep- 

 herds give the characteristic name of the gate 

 or Puerta de la Silla. We reached it about 

 seven. The morning was fine and cool, and 

 the sky till then seemed to favour our excursion. 

 I saw the thermometer keep a little below 14°-f-. 

 The barometer showed, that we were already 

 six hundred and eighty-five toises above the level 



* See my Obs. Ast. y Tom. i, p. 180. 

 + 1T2° Reaum. 



