1869.] 



with the Great Induction Coil. 



67 



The resistance of a single cell of this large Bunsen battery was found to 

 be -2585 B.A.U. 



In the following experiments the battery was arranged for intensity, and 

 used with the complete condenser of 750 square feet of tinfoil and 2000 

 square feet of paper in 1500 sheets. 



Number of cells 

 of battery. 



5 



10 

 15 

 20 



25 

 30 

 35 

 40 

 50 



Length of spark, 

 inches. 



complete condenser 12*0 



14-0 



17-5 



21-25 



23-0 



23-5 



26-0 



27'5 



28-0 to 29*0 



The longest spark yet obtained is therefore 29 inches in length. 



In order to ascertain whether any variation in the size of the condenser 

 (of which, as already stated, 1,2, 3, 4, 5, or 6 parts could be used) would 

 affect the length of the spark, a number of experiments were tried ; and it 

 will be noticed in the tabulated results that when half the condenser was 

 used the spark increased in length up to 20 cells, but not after. The experi- 

 ment of dividing the condenser and using one half led to a very serious 

 accident, and the coil was rendered useless for a time by the destruction of 

 the insulating material of a part of the primary coil ; the particular strands 

 affected threw out minute spicula of metal, which communicated with 

 each other, and the battery-current, instead of passing through 1257 yards, 

 now only traversed a very short length. The accident, however, proved to 

 be useful, inasmuch as it showed that the coil could be easily taken to 

 pieces and repaired in a comparatively short space of time. In the annexed 

 Table the experiments with the half of the condenser are marked with a 

 cross. 



Number of cells. 



10 



Length of spark, 

 inches. 



full condenser 12*00 



reduced £ 10*75 



one-half ov 

 reduced 



+ 



f 13*00 



a 



6 



4 

 (5 

 A 

 6 



13*50 

 13-00 

 11*75 



full condenser 14 00 



15-00 



1575 



r 2 



•educed J 



» 6 



