LIGHT. 135 



he admits that he could not succeed in procuring a vacuum, 

 but found electricity much less readily conducted or trans- 

 mitted by the best vacuum he could procure than by the ordi- 

 nary Boylean vacuum. 



Morgan found no conduction by a good Torricellian vac- 

 uum ; and, although Davy does not seem to place much reliance 

 on Morgan's experiments, there was one point in which they 

 were less liable to error than those of Davy. Morgan, whose 

 experiments seem to have been carefully conducted, operated 

 with hermetically-sealed glass tubes and by induced electricity, 

 while Davy sealed a platinum wire into the extremity of the 

 tube in which he sought to produce a vacuum. I have found 

 in very numerous experiments which I made to exclude air 

 from water, that platinum wires, most carefully sealed into 

 glass, allow liquids to pass between them and the glass ; and 

 this gives every reason to believe that gases may equally pass 

 through ; I have observed such effect in the gas battery when 

 it has been in action for a long period. Davy supposed that 

 the particles of bodies may be detached, and so produce elec- 

 trical effects in a vacumxn ; and such effects would more read- 

 ily take place in his experiments, where a wire projected 

 into the exhausted space, than in Morgan's, where the in- 

 duced electricity was diffused over the surface of the glass. 



M. Masson found that the barometric vacuum does not 

 conduct a current of electricity, or even a discharge, unless 

 the tension is considerable and sufficient to detach particles 

 from the electrodes ; and by adopting a plan of Dr. An- 

 drews, viz. absorbing carbonic acid by potash, M. Gassiot 

 has recently succeeded in forming vacua across which 

 the powerful discharge from the Rhumkorf coil will not 

 pass. 



The odour which- many metals, such as iron, tin, and 

 zinc emit, and the so-called thermographic radiations, we 

 can hardly explain upon any other theory than the evapora- 

 tion of an infinitesimally small portion of the metal itself. 



