146 



The BAKERIAN LECTURE was delivered by JOHN P. GASSIOT, 

 Esq., V.P.R.S., "On the Stratifications and Dark Bands 

 in Electrical Discharges as observed in Torricellian Va- 



The Lecturer gave an exposition of the substance of a Paper, 

 communicated by him under the above title, and illustrated his Lec- 

 ture by a repetition, before the Society, of the Experiments described. 

 The following is an abstract : 



The author refers to the stratified appearance of the electrical dis- 

 charge when taken from the terminals of a RuhmkoriFs induction- 

 coil in the vapour of phosphorus, and in highly attenuated gases, 

 first noticed by Mr. Grove (Phil. Trans. Part I. 1852, and Phil. 

 Mag., Dec. 1852). Having witnessed the experiments of Mr. 

 Grove, Mr. Gassiot in the same year examined the discharge in a 

 barometrical vacuum in which the mercury had been carefully boiled, 

 but he could not obtain any signs of stratification. These experi- 

 ments were subsequently repeated by several continental electricians, 

 whom he names, and who all describe the induction-discharge in a 

 barometrical vacuum as intensely white, and filling the whole tube 

 without stratification. 



After alluding to the experiments of the Rev. Dr. Robinson (Proc. 

 R. I. Acad., Dec. 1856), and to some recent improvements in the 

 construction of the induction-coil, the author proceeds to describe 

 apparatus which he had constructed for the more careful examination 

 of the character of the induction-discharge. His first experiments 

 were made on glass tubes about 1 inches long, in which the mer- 

 cury could be lowered or raised to any required level by means of the 

 air-pump. He also experimented with barometrical vacuums ob- 

 tained by inverting a tube of about 44 inches in length, filled with 

 boiled mercury, over a vessel containing that metal, and then sealing 

 the tube 2 or 3 inches above the barometrical height. 



The results obtained by these methods having been found un- 

 satisfactory, the author had recourse to that first suggested by Mr. 

 Welsh (Phil. Trans. 1856, p. 507), by which that gentleman con- 

 structed the large barometer at the Kew Observatory. Following 



