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resemblance they bear to an electric brush. But to the 

 electric phenomenon I am about to describe it is no mere 

 general resemblance, it is an actual likeness with every 

 feature identical. 



Before describing the phenomenon I may be allowed to 

 state how I came to notice it. It will be remembered that 

 in a former communication to this Society I ascribed the 

 phenomena of comets and the corona to a certain electrical 

 condition of the sun. Well, the peculiar appearance of Mr. 

 Brothers' photograph induced me to try if a brass ball, 

 brought into the condition I had ascribed to the sun, would 

 give off a corona presenting this appearance. 



The phenomenon is produced by discharging electricity 

 from a brass ball in a partially exhausted receiver. To do 

 this there is no second pole used, the objects which surround 

 the outside of the glass probably answering to this purpose. 

 In order to produce the desired appearance a certain relation 

 is necessary between the pressure of the air and the inten- 

 sity of the discharge. It is produced best when the receiver 

 is a glass globe insulated on a glass stand, the ball being 

 supported in its middle by a rod coated with indiarubber, 

 to prevent its discharging and spoiling the effect. It is only 

 negative electricity that is discharged into the globe. What 

 becomes of this electricity is not clear ; when a machine is 

 used it probably distributes itself on the inside of the glass, 

 and induces a corresponding charge on the outside. When 

 the coil is used it must escape back for I have had it going 

 for hours without any variation. 



There is great difficulty even when the apparatus is right 

 in producing the corona; using a large coil I just exhausted 

 the receiver till the pressure was equal to half an inch of 



