Intelligence and Miscellaneous Articles. 143 



to print the Essay at his own expense, and to present a copy to 

 the University Library, to the Library of St. John's College, and to 

 each of the four Examiners. 



C. Taylor, Vice-Chancellor. 



Gr. H. Darwix, Plumian Professor. 



Gr. Gr. Stokes. 



Kayleigh. 



ON ATMOSPHERIC ELECTRICITY. BY R. NAHRWOLD. 

 The author had shown in an earlier paper that electricity which 

 issues from a point into an earth-connected receiver, charges, in 

 preference, the floating dust particles in the enclosed space, which 

 are then quickly driven to the sides. If these sides are coated with 

 glycerine the particles remain there, and the space sooner becomes 

 free from dust than when allowed to settle gradually. 



He describes an experiment by which the action of electricity 

 on the dust diffused in the air is demonstrated in a striking manner. 

 A tubulated glass bell-jar, about 30 centim. in height and 20 

 centim. in diameter, was carefully cleaned and then coated on the 

 inside with glycerine. The bell-jar was inverted, and the upper 

 opening closed by a zinc sheet, which, with the layer of glycerine, 

 was in conducting communication with the earth. Through a hole 

 about 2 centim. in diameter in the centre of this lid a copper wire, 

 provided with fifteen fine sewing-needles, was fixed by an insulator. 

 This wire was made of two wires, of about 5 millim. diameter, 

 twisted together, and the needles are stuck in between these two 

 at a distance of 1 centim. apart and at right angles to the wire. 

 The copper wire was connected with one pole of a Topler's machine, 

 the other pole of which was to earth, so that when the machine 

 was \a orked the electricity issued from the needles into the bell-jar. 

 Tobacco-smoke could be blown through the lower aperture, so 

 that the bell-jar was quite opaque, and even the needles in the 

 centre could not be seen. "When now the machine was worked, 

 the smoke disappeared after two or three turns and the bell-jar 

 was as clear as before. 



Aqueous vapour, sal-ammoniac, phosphoric anhydride, and soot 

 could be used, but not so advantageously as tobacco-smoke. If the 

 inside was not coated with glycerine the same results were obtained, 

 but required a much longer time. 



The other results obtained by the author are as follows : — 



(1) It has been more conclusively proved than heretofore that 

 the electricity issuing from the points does not electrify the air 

 itself statically, but the dust in it, which consists of suspended 

 liquid or solid particles. 



(2) It has been shown that fine particles are driven away from 

 an ignited platinum wire, which are diffused in the surrounding 

 air ; and in this way air free from dust, which is not suited for 

 receiving electricity from points, becomes again capable of acquiring 

 a charge. 



