230 INDUCTIVE AFFINITY. 



silver, but not fused nitre, chloride or iodide of lead or solution 

 of sulphate of soda. With the addition, however, of a little 

 nitric acid to the sulphuric, the same single circle decomposes 

 all these bodies, and even water itself. The evolution of hydro- 

 gen gas on the negative metal is at the same time suppressed by 

 the nitric acid, which exerts a secondary action on that ele- 

 ment. 



8. The division of the connecting wire, and the separation 

 of its extremities to the most minute distance from each other, 

 is sufficient to stop all induction and the propagation of 

 the polar condition. In the most powerful voltaic battery 

 ever arranged, that which Mr. Daniell lately operated with, 

 consisting of seventy of his large cells, no induction was 

 observed to pass when the terminal wires were separated, not 

 more than the one thousandth of an inch, even with the flame 

 of a spirit-lamp or rarified air between them. Absolute contact 

 of the wires was necessary to establish the circulation. But 

 after contact was made, and the wires were heated to whiteness, 

 they might be separated to a small distance without the 

 induction being interrupted ; the space between them was 

 then filled with an arch of dazzling light, containing detached 

 particles of the wire in a state of intense ignition, which 

 were found to proceed from the zincoid to the chloroid, 

 the former losing matter, and the other acquiring it. So 

 highly fixed a substance as platinum is carried from pole to 

 pole in this manner ; but the transference of matter is most 

 remarkable between charcoal poles, which may be separated 

 to the greatest distance, and afford the largest and most bril- 

 liant arch of flame. A similar, although it may be an ex- 

 cessively minute detachment of matter, is found to accom- 

 pany the electric spark in all circumstances. Hence, the elec- 

 tric spark always contains matter. 



9. When terminal wires of a voltaic circle are grasped in 

 the hands, the circuit may be completed by the fluids of the 

 body, provided the battery contains a considerable number 

 of cells and the induction is of high intensity ; the nervous 

 system is then affected, the sensation of the electric shock being 

 experienced. 



10. The conducting wire becomes heated precisely in pro- 

 portion to the number of polar chains established in it, and 

 consequently in proportion to the size of the zinc plate ; and 



