Crosse's Experiments vnth the Voltaic Battety. 127 



quart basin on a circular piece of mahogany placed within the 

 funnel. When this basin was filled with a fluid, a strip of flannel 

 wetted with the same, was suspended over the edge of the basin 

 and inside the funnel which, acting as a syphon, conveyed the 

 fluid out of the basin, through the funnel, in successive drops. 

 The middle shelf of the frame was likewise pierced with an aper- 

 ture, in which was fixed a smaller funnel of glass, which sup- 

 ported a piece of somewhat porous red oxide of iron from Vesuvi- 

 us, immediately under the dropping of the upper funnel. The 

 stone was kept constantly electrified by means of two platina 

 wires on either side of it, connected with the poles of a Voltaic 

 battery of nineteen pairs of five-inch zinc and copper single plates, 

 in two porcelain troughs, the cells of which were filled at first 

 with water and ^ 1 ^ of hydrochloric acid, but afterwards with wa- 

 ter alone. I may here state, that in all my subsequent experi- 

 ments relative to these insects, I filled the cells of the batteries 

 employed with nothing but common water. The lower shelf 

 merely supported a wide-mouthed bottle, to receive the drops as 

 they fell from the second funnel. When the basin was nearly 

 emptied, the fluid was poured back again from the bottle below 

 into the basin above, without disturbing the position of the stone. 

 It was by mere chance that I selected this volcanic substance, 

 choosing it from its partial porosity ; nor do I believe that it had 

 the slightest effect in the production of the insects to be described. 

 The fluid with which I filled the basin was made as follows. 



I reduced a piece of black flint to powder, having first exposed 

 it to a red heat and quenched it in water to make it friable. Of 

 this powder I took two ounces, and mixed them intensely with 

 six ounces of carbonate of potassa, exposed them to a strong heat 

 for fifteen minutes in a black lead crucible in an air furnace, and 

 then poured the fused compound on an iron plate, reduced it to 

 powder while still warm, poured boiling water on it, and kept it 

 boiling for some minutes in a sand bath. The greater part of the 

 soluble glass thus fused, was taken up by the water, together 

 with a portion of alumina from the crucible. I should have used 

 one of silver, but had none sufliciently large. To a portion of 

 the silicate of potassa thus fused, I added some boiling water to 

 dilute it, and then slowly added hydrochloric acid to supersatu- 

 ration. A strange remark was made on this part of the experi- 

 ment, at the meeting of the British Association at Liverpool, it 



