154 Intelligence and Miscellaneous Articles. 



summer of 1863. But the fallacies arising from the tension of 

 aqueous vapour and from the air absorbed in water, as well as the 

 inconvenience of having to provide for the requisite fall, caused me 

 to discontinue the use of water, and to substitute in its stead mer- 

 cury as the most suitable liquid for establishing the truth, which I 

 had recognized by means of a water air-pump with an insufficient 

 fall. My paper of 1865 was written with reference to all liquids ; 

 in fact on p. 15 (rendered prominent by italics) I summed up 

 thus : — 



" The main fact which I have established in this paper may be 

 shortly stated to be, that if a liquid be allowed to run down a tube, to 

 the upper part of ivhich a receiver is attached by means of a lateral 

 tube, and if the height at ivhich the receiver is attached be not less than 

 that of the column of the liquid ivhich can be supported by the atmo- 

 spheric pressure, a vacuum ivill be formed in the receiver, minus the 

 tension of the liquid employed? 



I regret that the obviousness of the matter led me to refrain 

 from expressing myself in a more detailed manner, believing, as I 

 still believe, that what I wrote sufficiently described the construc- 

 tion of the water air-pump. 



In conclusion, Mr. Johnson's aspirator * for establishing a current 

 of air ought to be mentioned here. It was recognized by Professor 

 Hofmannf to act on the principle of the trompe, and, of course, 

 might have served as an air-pump, had it been noticed at the time 

 that the instrument would furnish the means of creating a vacuum . 

 And I may also draw attention to the tube % of a vacuum-pan, 

 through which the water is made to escape, which has served to 

 condense the steam of the boiling liquid. This no doubt would in 

 like manner have served as a complete water air-pump ; but it does 

 not appear that its use as such was discovered. 



London, January 22, 18/3. 



REPORT ON THE RESEARCHES OF M. ARN. THENARD CONCERNING 

 THE ACTIONS OF ELECTRIC DISCHARGES UPON GASES AND 

 VAPOURS. BY EDM. BECQUEREL. 



The publications of M. Arnould Thenard which the Academy 

 commissioned us to examine, have reference to the decomposition 

 effects produced by electric discharges on gases and vapours, espe- 

 cially carbonic acid. 



The effects due to the action of the electric spark on compound 

 gases are very complex ; for if, on the one hand, decomposition 

 may take place, on the other the separated elements, if they re- 

 main gaseous, tend to reconstitute the primitive compound. The 



* Quarterly Journal of the Chemical Society, vol. iv. p. 186(1852). 

 t Vide the same paper. 



\ Elements of Physics, by Neil Arnott, M.D. Longmans. 3rd edition. 

 London, 1828. 



