52 Questions Jor Solution relating to Meteorology, 



others, has devoted himself to this subject, and made extensive 

 investigations. These, however, are still in MS., and I regret 

 that I am unable to state the results. Besides this, the obser- 

 vations which M. Coraboeuf presented to the Academy of 

 Sciences are as directly to the point as could be desired, and 

 were conducted with a precision which left nothing to be de- 

 sired. 



This operation, carried on along the southern frontier of 

 France, during the years 1825, 1826, and 1827, embraces, in 

 the direction of the shortest distance, all the interval compre- 

 hended between the Ocean and the Mediterranean. Forty-five 

 triangles of the first order, many of which have their summits 

 on the highest points of the Pyrenees, join the fort of Sacoa, 

 near St Jean de Luz, at different points of the plain of Perpig- 

 nan, the elevation of which above the sea is so small as to be 

 reduced to two secondary triangles. All the angles have been 

 measured by M. Gambey's repeating circles, and by three series 

 of repetitions at the least. The same is the case with the ze- 

 nithal distances. Care has been taken, besides, to make these 

 observations only between 10 o'clock in the morning and 3 or 4 

 in the afternoon, in order to avoid the effects of the irregular 

 refractions, which appear near the horizon some hours after the 

 sun has risen, and a few hours before setting. The extent of 

 the atmospheric refraction, between each couple of stations, has 

 been deduced from a comparison of the reciprocal distances to 

 the zenith. As assistants in these important operations, M. Co- 

 raboeuf had Captain Peytier and Lieutenants Hossard and Testu 

 of the Geographical Engineers. 



The station of the Crabere occupies nearly the middle of the in- 

 terval which separates the ocean from the Mediterranean. The 

 eastern part of the chain of triangles has served to determine its 

 height above the Mediterranean ; the other part has afforded 

 this same height above the ocean. It is necessary to remark, 

 that the calculations can be made by a multitude of distinct 

 combinations, among which M. Coraboeuf has made choice of 

 three. He has ascended, in the first place, from the ocean and 

 the Mediterranean to the Crabere, passing by the only series of 

 summits of triangles which limit the chain towards the south. 

 In the next place, by choosing exclusively the northern sum- 



