Crosse'' s Experiments with the Voltaic Battery. 131 



Sulphate of zinc: 6. Water acidified with a minute portion of 

 hydrochloric acid : 7. Water poured on powdered metallic arse- 

 nic, resting on a copper cup, connected with the positive pole of 

 the battery. All these cylinders were electrically united to- 

 gether by arcs of sheet copper, so that the same electric current 

 passed through the whole of them. 



After many months' action, and consequent formation of certain 

 crystalline matters, which it is not my object here to notice, I ob- 

 served similar excrescences with those before described at the 

 edge of the fluid - in .every one of the cylinders, excepting the 

 two which contained the carbonate of potassa, and the metallic 

 arsenic ; and in due time a host of insects made their appearance. 

 It, was curious to observe the crystallized nitrate and sulphate of 

 copper, which formed by slow evaporation at the edge of the re- 

 spective solutions, dotted here and there with these hairy excres- 

 cences. At the foot of each of the cylinders, I had placed a paper 

 ticket upon the table, and on lifting them up, I found a little 

 colony oi insects under each, but no appearance whatever of their 

 havmg been born under their respective papers, or on any part of 

 the table. The third battery consisted of twenty pairs of cylin- 

 ders, each equal to a three inch plate. . Between the poles of this 

 I interposed likewise a series of six glass cylinders, filled with 

 various solutions, in only one of which I obtained the insect. 

 This contained a concentrated solution of silicate of potassa. 

 A bent iron wire, one fifth of an inch in diameter, in the form of 

 an inverted syphon, was plunged some inches into this solution, 

 and connected it with the positive pole, whilst a small coil of fine 

 silver wire joined it with the negative. 



After some months' electrical action, gelatinous silica enveloped 

 both wires, but in much greater quantity at the positive pole ; and 

 ill about eight months from the commencement of the experiment, 

 on examining these two wires very minutely, by means of a lens, 

 having removed them from the solution for that purpose, I plainly 

 perceived one of these incipient insects upon the gelatinous silica 

 on the silver wire, and about half an inch below the surface of the 

 fluid, when replaced in its original position. In the course of time, 

 more insects made their appearance, till, at last, I counted at once 

 three on the negative and twelve on the positive wire. Some of 

 them were formed on the naked part of the wires, that is, on that 

 part which was partially bare of gelatinous siUca : but they Avere 



