On the Electrical Phanomena exhibited in Vacuo. 1 8S 



and some I have made myself, that it is represented by a geo- 

 metrical progression; the decrements of temperature being 

 in arithmetical progression; and m three pure fluids that I 

 operated upon*, the ratio seemed nearly uniform for the same 

 immber of degrees below the boiling point; and (taking inter- 

 vals of 20 degrees of temperature) "SeQ^ 1 6. Upon this datum, 

 and considering the boiling points of mercury to be 600", that 

 of oil 54-0^ that of the chloride of antimony 340 ', and that of 

 tin 5000°, all above 52^^, and the elastic force of vapour of water 

 at this temperature to be equal to raise by its pressure about 

 •45 parts of an inch of mercury ; the relative strengths of va- 

 pour will be, for mercury 000015615, for oil 0016819, for 

 chloride of antimony 01692, and for tin 37015, preceded by 

 48 zeros f. 



It is not known whether the vapour fi-om solids follows a 

 similar law of progression as that from fluids, and these num- 

 bers are only given to show how minute the quantity of mat- 

 ter must be in vapours where its effects are distinct upon elec- 

 trical phenomena; and how much more minute it must be in 

 the case of mercury artificially cooled ; and almost beyond 

 imagination so in vapours from substances requiring very ele- 

 vated temperatures tor their ebullition. 



I made some comparative experiments to ascertain whether 

 below the freezing point of water, the diminution of the tem- 

 perature of the torriceUian vacuum diminished its power of 

 transmitting electricity, or of being rendered luminous by it. 

 To about 20° this appeared to be the case ; but between 20" 

 above and 20" below zero, the lowest temperature I could 

 produce by pounded ice and muriate of lime, it seemed sta- 

 tionary ; and as well as I could determine, the electrical phae- 

 noraena were nearly of the same intensity as those produced 

 in the vacuum above tin. 



Unless the electrical machine was very active, no light was 

 visible during the transmission of the electricity; but that this 

 transmission took place, was evident from the luminous ajv- 

 pearance of the rarefied air in the other parts of the syphon, 

 and from the diminution of the repulsion of the ball of the 

 tiuadrant electrometer attached to the prime conductor. When 

 trie machine was in great activity, there was a pale phospho- 

 rescent light above, and a spark on the mercury below, and 

 brilliant light in the common vacuum. A Leyden jar v:caJdif 

 charged could not be made to transmit its electricity by ex- 

 plosion through the cooled torriceUian vacimm, but this elec- 

 tricity was slowly dissipated through it; and when strongly 



* Water, chloride of |)hos|)horus, and iilcoliol or carburet of sii1],hiir. 

 •(• I am obliged to Charles Bubbage, Esq. F.R.S. tor these calculations. 



charged, 



