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II. Magnetic Survey of the East of France in 1869. JBy the Rev. Stephen J. Perry. 
Communicated by the President. 
Received July 13,- — Read November 23 , 1871. 
Magnetic Survey of the East of France, 1869. 
This survey, which occupied a considerable portion of the months of August and Sep- 
tember 1869, is a continuation of the series of observations made in the west of 
France during the preceding year. The instruments used were the same on both occa- 
sions, the only changes made for the second expedition being (1°) the substitution of a 
theodolite by Jones in lieu of Cooke’s transit-theodolite, which was slightly too heavy 
for carrying in the hand, and (2°) the procuring, through the kindness of Dr. Stewart, a 
second tripod stand similar to our own, which rendered the series of observations with 
two observers much more rapid than on the previous occasion. The observations were 
undertaken, as before, by the Rev. W. Sidgreaves and myself, the Vibrations and Deflec- 
tions falling to his share, and the Declination and Chronometer comparisons remaining 
in my hands, whilst the Dip was in general observed by both. The method of reduc- 
tion is almost identical with that adopted for the observations taken in the west of 
France. 
The geographical positions of the different stations have been calculated, as far as 
possible, from the data given in the ‘ Connaissance des Temps,’ but where this could not 
be done I have had recourse to the most reliable sources of information at my command. 
For the accurate determination of the positions of Mont Rolland (near Dole), of N. D. 
de Myans (near Chambery), of Mongre (near Villefranche-sur-Soane), of Iseure (near 
Moulins), and of our station at Marseilles I am indebted to the kindness of the Rev. 
N. Larcher, S.J., Membre de la Societe Meteorologique de France. The coordinates of 
Vaugirard were readily obtained from a good map of Paris, and for Issenheim and 
Monaco I have to depend on Cassini’s ‘Carte Generate de la France’ and on Philip’s 
‘ Imperial Atlas.’ The Imperial Observatory at Paris is chosen as the natural position for 
the origin of coordinates, in lieu of our central station of observation at Vaugirard, 
which lies on the outskirts of the city ; the resulting mean values will thus require no 
correction, and will be immediately comparable with those of most other observers. 
