1897.] Mr Townsend, On Electricity in Gases etc. 245 



attracted so little attention. The greater part of this paper is 

 devoted to an account of the electrification of gases which are 

 given off when a liquid is decomposed by an electric current, 

 being the most noteworthy result which I have arrived at while 

 examining the charges on newly prepared gases. Under certain 

 circumstances gases can be obtained by this method which have 

 an electrification, ten or twenty times greater than that which can 

 be given them by artificial processes. I find also that these gases 

 possess the remarkable property of forming a dense cloud when 

 they come into contact with moisture. The density of the cloud 

 increases with the density of the charge, and so distinctly does 

 this property manifest itself that a dry gas, charged even with a 

 density of electrification one-twentieth of that which can be 

 obtained, forms a distinctly visible cloud when it comes into the 

 moist atmosphere of the room. 



3. It is necessary here to describe some principles which will 

 be frequently used in the course of the following experiments. 

 In order to distinguish between cases when a gas, orthe dust or 

 spray it may contain, carries the charge it is sufficient to send the 

 gas through a series of fine gauzes or through a tube containing 

 glass wool ; by so doing not more than 20 or 30 per cent, of the 

 charge will be lost if the gas is electrified, but if the electricity 

 resides on the dust or the spray it will be completely removed by 

 filtering through the wool. In the case of a gas, the discharging 

 power, or the fraction of the charge left behind on any apparatus, 

 varies greatly according to the rate at which it is sent through, 

 being less for the greater velocities. There is another very 

 striking difference between the behaviour of a charged gas and 

 that of a collection of small charged particles when left in a vessel, 

 namely : the gas retains its charge for a considerable time, while 

 a collection of small charged particles rapidly discharges against 

 the sides of the vessel. This difference will also serve to dis- 

 tinguish between the two cases. 



4. Let /, fig. 1, be an insulated inductor, the outer surface 

 being made a conductor by covering it with tinfoil, and when it is 

 connected to the insulated quadrants of the electrometer the 

 motion of the spot of light (reflected from the mirror attached to 

 the needle), on the scale will register the quantity of electricity 

 entering or leaving /. If the air from the room be blown into / 

 from a blow-pipe bellows through a plug of glass wool the position 

 of the spot of light will not be affected, but if the tube containing 

 the wool be removed and the air be blown directly in from the 

 indiarubber tubing it will be found that the electrometer shows a 

 large positive charge on /. This charge was unable to pass 



