Experiments in Voltaic Electricity. 423 



copious stream of hydrogen. Examined by the microscope, a 

 metallic crystallization appears to shoot over t}ie surface of the 

 metal accompanied v ith prismatic colour. Heat tends to make 

 the globule less ,lni<l, bv evaporating the mercury and leaving 

 the oxide. Having- evaporated the water from a globule ex- 

 posed to the Voltaic action for 16 hours, the glass being much 

 heated, a series of small explosions accompanied with corusca- 

 tions of fire ap|)eared to take place from the residuum surround- 

 ing the mercury ; but as I have failed in reproducing this effect 

 by the same means, it is not impossible to have been an ocular 

 deception. On touching with the negative wire the globule 

 after it has been oxided by the positive, the oxide falls off in 

 scales, and the metal quickly reappears in its pristine brilliancy 

 and fluidity, a portion of oxide passing to the negative pole, and 

 no hydrogen gas given off, being absorbed by the globule — so 

 that it is easy to fix or make fluid the metal, which is best 

 done bv separate watch-glasses connected Avith each other by a 

 conducting substance — the positive globule will be fixed, the 

 negative fluid, and by reversing the glasses, both will be changed. 

 If the mercury has remained in contact with the negative wire 

 some time, and the positive is withdrawn so as to break the 

 connexion with the poles, the metal contracts and expands for 

 some seconds, as if to get rid of the hydrogen gas. The mer- 

 cury cannot be set in motion after having been coimected with 

 the negative for several minutes, until, having been first touched 

 by the positive, it is put in contact with the negative. The^e 

 effects take place when the glol)ule is subjected to the action of a 

 small trough charged with common water, but in a much less 

 degree. If the globule is very small, gas is given out by the 

 wire in contact with it, as well as by the other. If the water i» 

 warmed bv a lamp during the action of the wires on the mer- 

 cury, gas is more copiously liberated from both, and the oxide 

 instead of being dark is of a lemon colour ; but when the water 

 boils, the oxide is dissolved, the mercury is rendered clear, and 

 cannot be fixed; nor has the negative any attraction for it, nor 

 can it be coated with metal. In vacuo gas is given but by both 

 wires at the same time, and in a much greater quantity ; when 

 the air is admitted, the wires cease to give out more than before 

 it was exhausted. The watch-glass with its globule under com- 

 mon water being subjected to a stream of common electricity, 

 passing from one platina wire to the other, and ?iot intercepted ; 

 precisely the same effects took place as with the Voltaic trough, 

 but it required longer time. An -intercepted stream put the 

 j;lobule in most violent motion between the wires. No gas was 

 visible from either wire when the current of electricity was un- 

 D d 4 iuterruptedj 



