THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



JUNE 1863. 



LVI. On an Induction Coil of great power, and on the effects of 

 connecting Plates with the ends of the Secondary Coil. By the 

 Rev. N. J. Callan, D.D., Professor of Natural Philosophy in 

 St. Patrick's College, Maynooth*. 



ABOUT three years and a half ago I made an induction coil 

 of considerable power. The secondary coil, which was made 

 of No. 34 iron wire, consisted of three parts, two of which were 

 each about 2| inches, and the third 3 inches long. The entire 

 length of the secondary coil was about 8 inches, and the length of 

 the secondary wire about 150.000 feet. The mode of insulation 

 is nearly the same as that of the coil described in the Philoso- 

 phical Magazine for May 1859, except that thin sheet gutta 

 percha is used for insulating the spirals of one layer from those 

 of the adjoining layers. With three cells of the Maynooth 

 battery, in each of which the zinc plate was 4 inches square, the 

 coil gave sparks about 10 inches long between two pointed wires, 

 one connected with each end of the coil. With five cells of the 

 same size, the sparks were only IO5 inches, but were much louder 

 than the sparks produced by three cells. Within the last four 

 months I made a new primary coil nearly 3 feet long with a core 

 about 3 feet 6 inches in length, and improved the insulation 

 between the secondary coil and the primary, and also the insu- 

 lation of the three parts of the secondary from each other. 



Since these changes were made, this coil (the negative end 

 being connected with a plate containing a square foot of sur- 

 face, and the positive end with a pointed wire) gave sparks 7| 

 inches long with a single 4-inch cell of the Maynooth battery. 

 With two 4-inch cells the sparks were 12^ inches, and with 

 three cells of the same size they were 15 inches in length. 

 * Communicated by the Author. 



Phil. Mag. S. 4. Vol. 25. No. 170. June 1863. 2 F 



