Aecmnt ef on Ektirmtter, 31 



it to that pro(Iu£^ of the decompofition of the evaporating fubftance, which, having the lead 

 affinity for caloric, is rendered gafeous by the feparation of the reft, before it has acquired 

 fufficient caloric to fatisfy its refumed capacity. 



I might have added feveral fa£ls of inferior importance to the teftimony of thofe already 

 noticed, but I have thought it fufficient to fliow that the univerfal dictate of analogy, as to 

 the combination of caloric with fubftances whofe component parts have different degrees of 

 volatility, is fupported by the evidence of the moft important phenomena : and that we 

 have reafon, therefore, to conclude, that in every fuch cafe a refumption more or lefs com- 

 plete of the difcrete affinities of the conftituent parts for caloric muft take place, and that 

 in moft inftances, at leaft of evaporation, this refumption may be confidered as entire, and 

 the decompofition complete. It is certainly not inconceivable that there may be bodies, 

 the conftituent affinities of whofe parts may be fo great as to overcome the tendency of 

 their different affinities for caloric with any heat wc can apply.- It is not probable, how- 

 ever, that fuch exift among the fubftances with whofe conftitution we arc hitherto 

 acquainted, 



I am, SIR, 



Your's refpedfuUy, 



JOSEPH ASTLEY, 

 Edinburgh, Jan. 31, 1801. 



VI. 



j^cccuni of an EUBrometer. By ClT. C, L, Cadet*. 



HIS author, according to the ufeful cuftom of the French writers, gives a fliort pre- 

 fatory account of the eledrometers of Dufay with threads, Henley with the quadrant and 

 index. Canton by the fucceffive difcharge of a jar by fparks, Lane by the length of the 

 fpark, De Saujfure by the balls of Canton^ and Coulomb by the method of torfion ; to which 

 he might have added the floating inftrument of Nollet, the meafure of repulfion by weight 

 by ji. Brook, the extent of eleftric atmofpheres determined by the luminous point, by 

 Magioiio and Van Marum, the inclination of a thread at a given diftance by the fame 

 philofophers, and the gold leaf ele£lrometer by Bennet. He has purpofed to conftrudl an 

 inftrument capable of application to the meafurement of ftrong as well as weak elc£lricities, 

 without requiring any attention to fridlion or weight. Of this I fliall give the defcription 

 and account in his own words : 



•' Fig. I. Plate 11. In a glafs tube A, 18 or 20 inches long, is inclofed another ihorter 

 tube X, fealed at both ends. This tube contains a graduated fcale : one of the ends of thefe 



* Abridged from the author's paper in the Annalcs de Chimie XXXVII. £S. 



two 



