124 Electricity and Galvanism. 



this number, little heat and scarcely any light is to be detected, but 

 they are replaced by the actinic or tithonic phenomena, under whose 

 influence the magic results of the daguerreotype and photography 

 are produced. 



Whether electricity is distinct from this ether, or whether the 

 phenomena it produces when it is in what is called a free state, and 

 which are regarded as characteristic of its presence, depend upon 

 ether assuming vibratory movements differing in amplitude and velo- 

 city from those producing light, heat, and photographic effects, is 

 yet unknown. That there is a remarkable connection between light, 

 heat, and electricity, is, to say the least, quite certain ; for one can 

 never be excited without calling into existence one or both the others. 

 The conventional theory now generally adopted is, that electricity is 

 a compound imponderable form of matter composed of two elements, 

 denominated the positive and negative electric fluids, which, when 

 separated, produce analogous phenomena, but, when united, neutra- 

 lise each other so effectually that the existence of the neutral fluid 

 can never be detected, save by separating its component elements. 

 Whilst heat and light are readily detected when set free, by their 

 well-recognised effects, we have, in dealing with the subtle agent 

 whose properties we are investigating, to use a new series of tests. 

 These are either founded on the law that bodies similarly electrified 

 repel each other, or on the development of the phenomena of light 

 and heat. Nothing is easier than to demonstrate the existence of 

 electricity in ponderable matter, for it can scarcely be submitted to 

 any mechanical, chemical, or thermal influence without decomposing 

 the combined electric fluids. 



I will now abruptly draw the corner of my handkerchief over the 

 cap of the gold-leaf electrometer before me, and thus in an instant 

 shall decompose its neutral electricity, wiping away (as it were) the 

 positive fluid, and leaving its gold leaves negatively electrified, which 

 thus diverge to the extent of an inch or two. On touching the cap 

 with my finger, I give back the positive fluid in sufficient quantity to 

 neutralise the negative electricity of the gold leaves, and equilibrium 

 is restored. 



To shew the influence of chemical action in disturbing the normal 

 electric equilibrium, I have here a few glass vessels in which a little 



