402 SCIENTIFIC NEWS. 



measure heights not much differing from each other has 

 not much certainty when the two stations are on a 

 plane. 



With regard to the influence of meteors, it always acts 

 in the same direction, and causes the heights to appear too 

 small ; whence all observations are to be rejected which 

 were made in stormy weather. From all these consider- 

 ations it follows that in order to have the most exact 

 height of a mountain it will not be proper to take a mean 

 indifferently between all the observations made at dif- 

 ferent hours and seasons, as in this case the elevation 

 would always prove less than the truth. 

 Various re- ^^ extensive course of experiments by M.M. Biot and 



searches, dis- Arago upon the aflinitics between the different gases and 

 eovcnes, &c. light are not spoken of by the reporter, because M. Biot 

 purposes to give an extract himself. An abridgment of 

 Count Rumford's memoir on the dispersion of the light 

 of lamps through ground glass, likewise composes part 

 of the present report, which need not be given in this 

 place, because the Count's memoir has already appeared 

 in our Journal. 



Simple notices of inventions in Science and the Arts 

 which are entitled to honourable mention, are likewise 

 given in the present report, but as they contain no ac- 

 counts of the methods or processes, it has not been 

 thought necessary to repeat them here. Since its last 

 public sitting the Class has published the first volume of 

 Various publi- Memoirs presented by learned Foreigners (Savans Etran- 

 cations. g^rs), and the sixth volume of its own Memoirs. The 



following volumes will be published every six months, 

 beginning with July last. The first volume of La Meri- 

 dienne de Dunkerque, base du Systemc Metrique decimal. 

 This work contains all the authorities, observations, and 

 methods of calculation which have fixed the two funda- 

 mental unities of the Metrical System, namely, the Metre 

 and the Kilogramme. 



Several members have published new works, or new 

 editions of works already known, in which important 

 additions are found. Among these M. Legendre has 

 published a sixth edition of his Geometry, and Lacroix a 



second 



