Mr. J. P. Gassiot on Experiments made ivith Ruhmkorff's Coil. 99 



6. I coated about two-thirds of the inside of a Berlin glass 

 beaker of 4 inches depth by 2 inches width with tin-foil, leaving 

 about 1"5 of an inch of the upper portion uncoated. On the 

 plate of the air-pump I placed a glass plate, and on it the glass 

 beaker, covering the whole M-ith an open-mouth glass receiver, 

 on which was placed a brass plate having a thick wire passing 

 through collars of leather; the portion of this wire within the 

 receiver was enclosed in an open glass tube. One end of the 

 secondary coil was attached to the wire and the other to the 

 plate of the air-pump. As the vacuum improves, the effect is 

 truly surprising; at first a faint, clear, blue light appears to 

 proceed from the lower part of the beaker to the plate ; this gra- 

 dually becomes brighter, until by slow degrees it rises, increasing 

 in brilliancy until it arrives at that part which is opposite or on 

 a line with the inner coating ; the whole being intensely illumi- 

 nated, a discharge then commences from the inside of the beaker 

 to the plate of the pump in minute but diffused streams of blue 

 light ; continuing the exhaustion, at last a discharge takes place 

 in the form of an undivided continuous stream overlapping the 

 vessel, as if the electric fluid was itself a material body running 

 over. When first witnessed, it appears at the moment impossible 

 to divest the mind of such a conclusion. 



7. If the position of the beakers is reversed by placing the 

 open part on the plate of the air-pump, and the upper wire is 

 either in contact or within an inch of the outside of the vessel, 

 streams of blue lambent flame appear to pour down the sides to 

 the plate, while a continuous discharge takes place from the 

 inside coating. 



8. A thin piece of tale or very thin glass coated on one side with 

 tin-foil, and the other having a figure as a star, cross letters, &c., 

 also of tin-foil, produces a very beautiful experiment. The larger 

 coating is attached to one end of the coil ; the wire of the other 

 is then by means of a vr ■- rod brought into contact with the 

 figure of the star, cross, &c., which is immediately illuminated in 

 the most brilliant manner, and the well-known odour of ozone, as 

 from the electrical machine, is perceptible to an unusual degree. 



9. When the air in a glass tube 4 feet 2 inches long and 

 2 inches in diameter, similar to those used for the aurora expe- 

 riments, is exhausted, the ' discharge takes place, illuminating 

 the entire tube. 



I will not occupy your valuable s])ace with any further detail 

 of experiments made by myself with this really beautiful instru- 

 ment, the constniction of which reflects so much credit on the 

 ingenuity and talent of J\I. Ruhmkorff. 

 I am. Gentlemen, 



(Jlnpliiim Common, Yours obediently, 



Jttiiuiiry n, 1854. JoHN P. GaSSIOT. 



