2 1 6 Mr. Crosse on tlie Tension Spark from the Voltaic Battery. 



lity of obtaining a spark between the poles of a voltaic battery 

 before the circuit is completed. Were you to see the action of 

 my unfinished water battery of 1626 pairs of zinc and copper 

 cylinders, you would allow the question to be set at rest. 

 I take a small glass stick, and tie on it, with waxed silk thread, 

 very securely, two wires of platina, with the two extreme ends 

 ready to be plunged into two cups of mercury connected with 

 the opposite poles of the battery : the two other ends of the 

 wires are brought to the distance of about y^th of an inch 

 from each other, as below. 



D 



H 



A B, CD, two platina wires secured on the glass stick 

 E, F, G, H at the parts E, F, G, H. The two nearest ends 

 of the wires approach each other at B, C to about the di- 

 stance of Tff^th of an inch. I say about, for I have no in- 

 strument to measure it with accuracy, nor is it of any conse- 

 quence, as the cells of that battery are not by any means so well 

 insulated, as that the above distance should be taken as a 

 test of intensity of the battery. The moment the connexion is 

 made with the poles of the battery, a small stream of fire takes 

 place at the interval between B and C, which I have kept up 

 for many minutes, nor did it appear inclined to cease. This 

 experiment never fails, but with a much greater number of 

 plates, each pair not being separately insulated, it would never 

 succeed. To expect to produce a spark or visible current 

 under similar circumstances with the above would be hopeless, 

 except with a considerable number of pairs of plates, each pair 

 being separately insulated. With 1200 pairs I have succeeded, 

 and with 10,000 or 20,000 the distance at which it would 

 strike would be very great, comparatively speaking. 



I showed a friend the other day about twelve inches of 

 iron chain illuminated pretty strongly by the passage of 

 repeated shocks of my large electrical battery through it, 

 charged by the water battery alone. The intensity was so 

 great as to keep up a constant dance of pieces of silver-leaf 

 between two plates connected with the opposite poles. The 

 reason why Professor Daniell's water battery, which you em- 

 ployed in some of your experiments, failed, was first, that the 

 cells were not separately insulated, and secondly, that they 

 were too few in number. I presume it was the water battery 

 which I once saw used at the Royal Institution, the intensity 

 of which was very feeble. 



I do wish you could manage to pay me a visit, and see the 



