Royal Academy of Sciences of Paris. 141 



have considerable importance, as showing the intimate connection 

 between the electric and chemical systems. 



Oxides of Barium. On the 13th June, M. Despretz stated that 

 the hydrate of barytes, which has been generally said to resist heat, 

 is decomposed at a sustained red heat. This fact, which completes 

 the series of experiments tried with lime, magnesia, and strontium, 

 proves that no oxide of barium will retain water at a high tempe- 

 rature. 



Azote and Iron. At the same meeting, M. Despretz also stated, 

 that iron, at a red heat, subjected to the action of azote gas, is sen- 

 sibly increased in weight ; it disengages azote when dissolved in the 

 acids. 



Sulphates. M. Despretz also remarked, that all the sulphates 

 which are not liable to be decomposed by heat alone, disengage 

 sulphur, when acted on by carbon or hydrogen gas at a strong red 

 heat. 



GEODESY. 



Heights of the Pyrenees. On the 4th April, M. Puissant presented 

 to the Academy a report on a memoir by M. Coraboeuf, entitled 

 * Sur les Ope'rations Ge'odesiques des Pyrenees et sur la Cornparaison 

 du Niveau des deux Mers.' The object of this paper was to fix with 

 certainty the heights of several of the summits of the Pyrenees, and 

 to determine the long-contested question as to whether the waters 

 of the Mediterranean are precisely on the same level as those of the 

 ocean both being, of course, considered as in a state of perfect 

 tranquillity. The report stated that the mode of operation, adopted 

 by M. Coraboeuf and his associates, was such as almost to preclude 

 the possibility of any important error existing in his conclusions. 

 His trigonometrical observations were always made in the most 

 favourable state of the atmosphere, and the calculations result- 

 ing from them worked with scrupulous fidelity. The results 

 obtained by M. Coraboeuf generally coincide with those mentioned 

 in the * Base du Systeme metrique decimal ' the greatest difference 

 being O m 24 on a distance of 9514 m 78, and that but in one in- 

 stance, the distance from Espira to the southern point of the base of 

 Perpignan. In calculating the heights, M. Coraboeuf made use of 

 two tables, which he has annexed to his memoir the one being the 

 height above the Mediterranean, as observed by him on the eastern 

 side, and the other the height above the ocean on the western side. 

 The medium between these two calculations has been adopted as the 

 definitive height. The greatest difference found between the two 

 heights is that of Gardan de Montagu, which varies 2 m 64 ; but this 

 is to be accounted for by the great difference of the level between 



