Prof, l^ndall on the Currents of the Leyden Battery. 227 



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 electri- 

 cities, 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 

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

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

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

 ing to inquire whether frictional electricity produces analogous 

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

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

 of Berlin. 



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 spark 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 discs were taken. Each disc confained 75 feet of copper 

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

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

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

 disc 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 ])latinum wire, 10 inches 

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

 sent through the other sj)iral, 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 6 inches apart, 

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

 aroused in the othoi- was suflicient to deflagrate a thin platinum wire 

 4 inches in length. 



We have every reason to suppose that the secondary current thus 

 developed is of the same nature as the primary which produced it; 

 and hence we may infer, that if we conduct the secondary away 

 and carry it through a second spiral, it, in its turn, will act the 

 part of a primary, and evoke a tertiary current in a sj)iral brought 

 near it. This was illustrated by experiment. First, two spirals 

 were placed opposite to each other, through one of which the cur- 



