Skey. — On Conductivity. 581 



Note 3. 

 Gold leaf as on the surface of a weak cyanide solution is 

 at first strongly positive to the same kind of gold leaf as im- 

 mersed in this solution ; but it very shortly becomes negative 

 thereto, and remains so until dissolution breaks the voltaic 

 connection. The singularity of this circumstance is obvious, 

 when we consider that gold on the solution is far more rapidly 

 attacked by cyanide than is gold which is beneath the surface. 

 This is an interesting fact that requires explanation. 



Note 4. 

 Kerosene, gasoline, and hydrocarbons generally, when 

 placed over gold leaf that rests on the surface of a cyanide 

 solution, do not sensibly interfere with the dissolution of that 

 gold, if only oxygen has free access to the hydrocarbon used. 

 This result shows — (1) That the rapid dissolution of gold 

 leaf as placed on the surface of cyanide solutions is not in 

 part due to the action thereon of " air voltaic circles," as is 

 stated by Professor Faraday in the lecture referred to (the 

 atmosphere itself being cut off) ; (2) that these hydrocarbon 

 oils are pervious to air, or at least the oxygen of it ; and (3) 

 that a very minute quantity of oxygen is as effective for pro- 

 moting or assisting towards the rapid dissolution of gold leaf 

 resting on such solutions as is an unstinted supply of it. 



This concludes the notes that I hope shortly to embody in 

 two papers for this Society at an early date. 



Art. LX. — On the Conductivity of certain Substances Jiitherto 

 supposed to be Non-conducting for Voltaic Electricity. 



By William Skey, Analyst to the Department of Mines. 



[Read before the Wellington Philosophical Society, 17th February, 1897.] 



It is generally supposed, and with apparent good reason, that 

 all substances may be polarised, but I do not know that it has 

 yet been proved or asserted that generally all substances are 

 conductors of voltaic electricity, but that such is the case the 

 following results of certain experiments of mine appear to 

 show : — 



(1.) A piece of copper wire, heated in an oxidizing flame 

 until its metallic aspect has quite disappeared over the whole 

 surface, then placed in a voltaic circuit with mercury as the 

 anode and cathode, does not break the current, or even reduce 

 it to any notable extent. 



