312 



by corresponding altitudes : and at night, one 

 of those reddish vapours, which do not affect 

 the hygrometer in the lower regions of the at- 

 mosphere, veiled the stars. 



This phenomenon was the more extraordinary, 

 as in other years it often happens, during three 

 or four months, no trace of clouds or vapours 

 is to be seen. I had a complete observation of 

 the progress and of the end of the eclipse. I 

 determined the distance of the horns, or the 

 differences of altitudes and azimuth, by the 

 passage over the threads of the quadrant. The 

 end of the eclipse was at 2 h 14' 23*4", mean 

 time at Cumana. The result of my observation^ 

 calculated according to the ancient tables, by 

 Mr. Ciccolini at Bologna, and by Mr. Tries- 

 necker at Vienna, has been published in the 

 Connoissance des Temps*. The result did not 

 differ less than 1 ' 9" in time from the longitude 

 I had determined by the chronometer ; but cal- 

 culated afresh by Mr. Oltmanns, by the new 

 lunar tables of Burg, and the solar tables of 

 Delambre, the eclipse and the chronometer 

 agreed to 10" nearly. I cite this remarkable 

 instance of an error reduced to one seventh 

 by the use of the new tables, to remind tra- 

 vellers how much it is their interest to note 

 and publish the most minute details of their 



* Year 9, p. 142. Zach, Mon. Corresp., Vol. \, p. 596, 

 (See also note A. at the end of this fourth book). 



