42 Mr. R. Phillips on Frictional Electricity. 



may be supposed that the increased effect, which is uniformly 

 observed with hot water, may be only the result of an improved 

 insulation, I take the following from the notes of the experi- 

 ments, which extract I omitted at the time of publication as not 

 then appearing of much importance. 



The stream of water, by flowing along the arm of the tin pipe 

 (108.), produces a breeze through the pipe ; and the current of 

 air thus carried forward must convey away the negative elec- 

 tricity, as from the circumstances of the experiment there is no 

 other outlet for the negative electricity. Accordingly, on nearly 

 closing the orifice of the shorter arm of the tin pipe with a bung, 

 the. production of the positive electricity is diminished; and so 

 is also the current of air, which, however, continues to escape in 

 some measure from the other end of the pipe. This is precisely 

 similar to what happens with an ordinary electric machine, the 

 prime conductor of which soon ceases to afford much electricity 

 if the negative electricity is retained on the rubber. Now I 

 observed, when cold water was discharged from the fountain, 

 that on closing the shorter arm of the tin pipe, the quantity of 

 positive electricity transmitted to the electrometer was scarcely 

 diminished, but that with hot water the effect was very striking. 

 The only explanation of this is, I think, the following : the 

 quantity of air which passed through the tin pipe being the same 

 under similar circumstances with either hot or cold water, that 

 with the cold water, the air which continued to escape after the 

 bung was inserted, was nearly sufficient to convey away all the 

 negative electricity ; while with the hot water so much negative 

 electricity was produced, that the same quantity of air was quite 

 inadequate for its removal. 



Perhaps the reason why water is always positive when rubbed 

 on a solid is, that its particles are so much more easily abraded 

 than that of solids, that the abrasion of the solid takes no part 

 in producing the electricity, and consequently the order of the 

 + and — alternations of the solid rubber does not enter into 

 the final result. 



Although a stream of air in falling on a solid produces nothing 

 answering to abrasion, yet it is conceivable that a stream of air, 

 in flowing along such a thing as a channel of ice, might strike 

 upon some projecting portions, and thereby produce such a con- 

 densation of air about them as to cause their liquefaction ; but 

 such cases, if any, obviously belong to the abrasion of a fluid, 

 and may produce electricity. The friction of air in an orifice 

 may be explained in a similar way. The air suffers a condensa- 

 tion in striking on the sides of the orifice ; and the heat which 

 is produced by this condensation must be more or less absorbed 

 by the walls of the orifice, thus occasioning a corresponding 



