194 On the Arcs perpendicular to the Meridian^ 



extreme stations. This advantage, however, was not derived 

 by the Austrians, who, apparently from the different states of 

 preparation of different parts of the arc between Munich and 

 Czernowitz, determined it in separate portions independently 

 of each other. Thus, in May, 1822, the difference of longi- 

 tude between the observations of Vienna and Buda was ascer- 

 tained by explosions of powder, at the chapel of St. Rosalia, 

 on a mountain on the frontiers of Austria and Hungary, seven 

 and a half German miles from Vienna, the apparition of which 

 was noted at Vienna, and by chronometers stationed on a 

 mountain near Dotis, in Hungary ; and by other explosions 

 on the Nasnal, six German miles from Buda, the apparition ot 

 which was noted by the chronometers at Dotis, and at the 

 observatory at Buda. The observations were made on the 

 nights of the 12th, 21st, 22nd, and 23rd of May, giving, as 

 the result of ten comparisons, 10' 40",699. A second trial 

 was made in August of the same year, in which an alteration 

 was made in the locahty, but not in the arrangement of the 

 intermediate stations, by which twenty-eight comparisons were 

 effected of thirty attempted, on the nights of the 17th, 18th, 

 and 19th ; the result was 10' 40",7, which may be considered 

 as identical with the former determination, and is a good spe- 

 cimen of the confidence to which this method of determining 

 differences of longitude is entitled. In the same month, but 

 not on the same days, the difference of the meridians of the 

 observatories of Vienna, and Bogenhausen near Munich, was 

 ascertained, by a similar arrangement of intermediate stations, 

 to be 19' 05",202. No report has yet been made of the signals 

 between Buda and Czernowitz. 



The arrangement adopted on the French portion of the 

 parallel is an extension of that introduced by the Austrians (of 

 substituting chronometrical for astronomical stations) to all 

 the stations intermediate between the extreme ones of the 

 total arc, where alone consequently the absolute time is deter- 

 mined. It may be regarded as a mode of covering an arc of 

 considerable extent, where there is no deficiency of individuals 

 capable of noting correctly the apparition of signals by a chro- 

 nometer, but with the smallest possible number of observers 

 competent to. determine absolute time, — rather than as, on the 



