now measuring on the Continent. 185 



seen, in 1822, is united in M. Nicollet's Memoir to the ampli- 

 tude between Mont Cenis and Milan, ascertained in the foUow- 

 in^ year, — making but one arc between the observatory at 

 Geneva and the Dome of Milan, — the amplitude of which is 

 3' 08",76 + 9' 00",81 = 12' 09^57. 



In August, 1824, by direction of the Austrian government, 

 the difference of longitude between the observatories of Milan 

 and Padua was determined as follows by signals made on the 

 Monte Baldo : — 



Mean of four series . 40 signals . . . 10' 43",277 

 Reduction to the Dome at Milan ... — 0'',606 



Reduction to the steeple of Sainte Justine at Padua + 2 ',712 



Diiference of longitude between the Dome of Milan 



and the steeple of Sainte Justine at Padua . 10' 45'',383 



There remains but a single portion more, namely, that between 

 Padua and Fiume, to complete the entire amplitude between 

 Marennes and Fiume ; this portion has been measured by 

 signals on Monte Baldo, visible at the same time at Milan, 

 Padua, and Fiume ; but the results are not yet reported. 



The rate of the clock, and its difference on sidereal time, 

 was ascertained at each of the temporary observatories, by 

 zenith distances of the principal stars, east and west of the 

 meridian, never under 30° or above 60° of altitude. Several 

 stars were observed on the same night whenever the weather 

 permitted, and the clocks were always established several days 

 before the signals were commenced. As far as was possible, 

 the apparition of the signals was noted by the clock itself; but 

 when not visible from the spot where the observatory, was 

 placed, two chronometers were always employed, which were 

 compared with the clock immediately before and immediately 

 afler the signals. 



We have been thus particular in relating in detail the pro- 

 ceedings by which the celestial amplitude was ascertained, for 

 t-wQ reasons ; first, because it i^ the first ti?ne that the attempt 



