1855.] on the Currents of the Ley den Battery. 133 



theless advantageously make use of the language of these theories in 

 bringing the facts of a science before a public audience ; and in 

 speaking of electricity, the speaker availed himself of the convenient 

 hypothesis of two fluids, without at all professing a belief in their 

 existence. A Leyden jar was charged. The interior of the jar 

 might be figured as covered with a layer of positive electricity, 

 and the exterior by a layer of negative electricity ; which two 

 electricities, notwithstanding their mutual attraction, were prevented 

 from rushing together by the glass between them. When the 

 exterior and interior coating are united by a conducting body, the 

 fluids move through the conductor and unite ; thus producing what 

 is called an electric current. The mysterious agent which we darkly 

 recognise under this symbol is capable of producing wonderful 

 effects ; but one of its most miraculous characteristics is its power 

 of arousing a transitory current in a conductor placed near it. The 

 phenomena of voltaic induction are well known ; and it is interest- 

 ing to inquire whether frictional electricity produces analogous 

 phenomena. This question has been examined by Dr. Henry, and 

 still more recently by that able and experienced electrician M. Riess, 

 of Berlin. The researches of these gentlemen constituted the sub- 

 ject of the evening's discourse. 



A wooden cylinder was taken, round which two copper wires, 

 each 75 feet in length, were wound ; both wires being placed upon 

 a surface of gutta-percha, and kept perfectly insulated from each 

 other. The ends of one of these wires were connected with a 

 universal discharger, whose knobs were placed within a quarter of 

 an inch of each other ; when the current of a Leyden battery was 

 sent through the other wire, a secondary current was aroused in 

 that connected with the discharger, which announced itself by a 

 brilliant sjiark across the space separating the two knobs. 



The wires here used were covered externally with a sheet of 

 gutta-percha ; and lest it should be supposed that a portion of the 

 electricity of the battery had sprung from one wire to the other, 

 two flat disks were taken. Each disk contained 75 feet of copper 

 wire, wound in the form of a flat spiral, the successive convolutions 

 of which were about two lines apart. One disk was placed upon 

 the other one, the wire being so coiled that the convolutions of 

 each disk constituted, so to say, the impress of those of the other, 

 and the coils were separated from each other by a plate of varnished 

 glass. The ends of one spiral were connected with the universal 

 discharger, between whose knobs a thin platinum wire, ten inches 

 long, was stretched. When the current of the Leyden battery was 

 sent through the other spiral, the secondary current, evoked in the 

 former, passed through the thin wire, and burnt it up with brilliant 

 deflagration. A pair of spirals were next placed six inches apart, 

 and a battery was discharged through one of them ; the current 

 aroused in the other was sufficient to deflagrate a thin platinum wire 

 four inches in length. 



