Academy of Sciences in Paris. 563 



water at the ordinary temperature ; it oxidises at a high tempera- 

 ture, and is converted into magnesia; slowly when it is in rather 

 large pieces, but when it is in fine dust, it burns with great splen- 

 dour, throwing out sparks like iron in oxygen. 



Perchloric acid. March 14. M. Serullas communicated to the 

 Academy the result of an experiment which he had just made on 

 perchloric acid. He stated that he had observed that this acid, 

 when combined with several of the vegetable alkalies, formed acid 

 salts in a perfect state of crystallization, which induced him to 

 endeavour to obtain perchloric acid in a concrete form, in order to 

 strengthen his theory of the general tendency of concrete acids to 

 generate acid salts. He had already tried the experiment with 

 potash, but had obtained only a neutral salt. 



He now distilled the perchloric acid with about two or three times 

 its weight of concentrated sulphuric acid. This, when in a state of 

 ebullition, occasioned the separation of chlorine, which gave a yellow 

 colour to the liquid, and at the same time of perchloric acid, which 

 was received in a tube and surrounded with ice ; part of this acid 

 was in a liquid, and part in a crystallized. In this state it does not 

 contain any sulphuric acid, the temperature not being sufficiently 

 high to admit of its distillation ; when exposed to the air, white and 

 very thick vapours are emitted ; when poured into water, each drop 

 produces a sound similar to that of red-hot iron dipped into the 

 liquid. The solid portion crystallizes in transparent prisms, and 

 the liquid part, when exposed to the air in a watch-glass, is rapidly 

 volatilized, acquiring solidity, until it totally disappears. M. Se- 

 rullas had not ascertained whether it was entirely free from water. 



GEOLOGY. 



Elevation of the Morea. In a paper communicated to the 

 Academic des Sciences, on the 31st January, containing a series 

 of geological observations made by M. Boblaye, in the Morea and 

 in Egina, it is stated that there are positive proofs of the whole 

 soil having risen considerably, not in a gradual or continuous man- 

 ner, but by sudden starts, so that the grounds abandoned by the 

 sea are marked out in steps or layers in irregular gradation. 



Hwnboldt's Map of Heights. On the 21st March, M. de Hum- 

 boldt exhibited to the Academy a map, which he calls Esquisse 

 Hypsometrique des rauds des montagnes et des ramifications de la 

 Cordillere des Andes depuis Cap Horn jusqu'k 1'Isthme de Panama 

 et a la chaine littorale de Venezuela.' It extends from 62 to 84 

 degrees of west longitude, (Mer. Paris,) and from 21 degrees south 

 to 11 north latitude. In a verbal explanation which he gave of it, 

 he observed that notwithstanding the numerous men of science 

 who had traversed the Isthmus, no positive information had been 

 obtained respecting the heights of the mountains which continue 



