Chemical Science. 183 



but tlie phenomena were just as before, and both the rubbing 

 and rubbed surface shone brightly. Afraid of the metal about 

 the umbrella, it was thrown down, and M. AUemand went on his 

 way, rubbing his hat on the sleeve of his coat; but in this way 

 only rendering the light brighter. The thunder was more frequent 

 than before, but still at some little distance. The crown of light 

 continued until M. Allemand arrived near Motiers, and he at- 

 tributed its cessation to the high poplar trees in the neighbour- 

 hood of that place. 



Stopping at Motiers only a short time, he took a guide with 

 a lantern to find the umbrella. Having done so he sent back 

 the man, and went on himself towards Fleurin. 



As the tempest had diminished, he used the umbrella; and 

 as soon as the light of the lantern was sufficiently removed, he 

 kgain remarked luminous appearances. These occurred at each 

 end of the whalebone ribs, on the metal point which terminates 

 them ; the light was not so bright as the electric star, but were 

 brilliant points like a yellow red metal, highly polished, and 

 would, M. A. remarks, have appeared very beautiful if he had 

 been collected enough to admire them. 



M. Allemand explains these effects by supposing the atmosphere 

 sursaturated with electricity, and that a portion of it was con- 

 tinually passing to the ground, through his hat, umbrella, and 

 himself. 



16. On Voltaic Electricity, by M. Pictet.— The following 

 thoughts on Voltaic Electricity are by M. Pictet of Geneva. 



In reflecting on this subject, we have been led to a few con- 

 siderations that tend to explain the well-known fact of the great 

 heating power, and weak chemical action of the voltaic appa- 

 ratus, with few plates of large surface, compared to the appa- 

 ratus of many small plates which produces little heat, but has 

 much decomposing power. 



Two very different actions maybe distinguished in the voltaic 

 apparatus. l.The chemical action of the fluid which, in at- 

 tacking the plates, disengages the electro-caloric, and in quan- 

 tity greater as the action is more rapid. 2. An electro-motive 

 force resulting from the reciprocal action of the two metals of 

 each pair of plates, and by which the electro-caloric is pat in 

 movement in a direction according to the position of the plates. 



This electro-motive force is probably exerted in a series of ac- 

 tions separated by very short periods of time, or time prescribed, 

 and equal in each apparatus for a time given. The existence 

 of these vibrations is indicated by the characteristic trembling 

 produced by the voltaic action on the nervous and muscular 

 system by the galvanic shock. Let us suppose 100 of these vi- 

 brations in a second. A little more or less is of no consequence. 



Ill the voltaic apparatus, with few plates and large surface. 



