50 Mr. Noad on the peculiar Voltaic Conditions. 



wires had become accidentally wetted with the acid, and it was 

 sufficiently evident that this had interfered with the result, for 

 when they were carefully dried the experiment always suc- 

 ceeded. When a wire has been once used, the property is de- 

 stroyed in it, at least for a longtime. The acid should be quite 

 free from nitrous acid vapour, and I have found it better, in 

 order to insure this, to heat it gently for some time, using it 

 when quite cold, after diluting it with the requisite quantity 

 of distilled water. Observing these precautions in all the 

 experiments I shall here describe, I have no doubt that any 

 person who feels inclined to repeat them will arrive at results 

 similar to mine. The iron wire I employed was y^^^h of an 

 inch in diameter, the platina much less. 



Suppose three glasses arranged, as in the sketch, before a 

 galvanometer, the platina and iron wires immersed in their 

 respective glasses, and connected with the instrument in such 

 a manner that the iron shall be active. Let the iron glass be 

 united to the one next to it by a bent wire; now take another, 

 similarly bent, clean piece, and dip one endjlrst into the iron 

 glass, and then gradually bring the other end into the platina 

 glass, and it will be found inactive. At the moment of immer- 

 sion, a slight deflection of the needle will be perceptible, but 

 this will soon cease ; and after it has taken up its usual position, 

 rapidly break and renew the contact of the platina or iron 

 extreme wire with its cup : not the slightest further oscillation 

 will ensue, which decisively proves that no electrical current 

 is passing, although a strong one is called forth by the action 

 of the extreme iron wire. If a bent platina wire, not larger 

 than a pack-thread, or a strip of any other metal, is made to 

 connect the two glasses, an immediate deflection of the needle 

 takes place, greater or less in proportion as the metal is more 

 or less acted on. I have repeated this curious experiment fifty 

 times in the presence of various persons with the same result, 

 never having been able to trace the slightest electrical current 

 across the inactive wire, and never having met with any other 

 metal beside that refused the passage. If the connecting wire 

 with both ends active is now removed, and another new and 

 clean one substituted, observing the same order in immersing its 

 ends, the extremity nearest the platina glass will be rendered 

 inactive, and the same will result with any number of arrange- 

 ments. The galvanometer I have employed is a very delicate 

 one; the needle is astatic and suspended by a single hair; it 

 was constructed for me by Messrs. Knight of Foster Lane. 



When the needle of the galvanometer is quite still, let 

 either of the inactive ends be touched at a single point with 

 any metal on which the acid is capable of exerting an action, 



