1855.] Prof Faraday on Ruhmkorff*s Apparatus. 139 



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WEEKLY EVENING MEETING, 



Friday, June 8. 



The Duke op Northumberland, K.G. F.R.S. President, 

 in the Chair. 



Professor Faraday, D.C.L. F.R.S. 

 On Ruhmkorff's Induction Apparatus. 



This apparatus is known to consist of a soft iron core, intended to 

 act magnetically, around which there is a coil of coarse copper wire, 

 to be connected at pleasure with few or many cells of a voltaic 

 battery ; and external to this is a second coil of much thinner copper 

 wire, having great length, in which the peculiar currents of the 

 apparatus are to be produced. The coils of the wires are insulated 

 from one another by a very careful mode of preparation. The 

 inner, called the primary coil, is supplied with an automatic con- 

 trivance, so that when the battery is connected with it, the con- 

 tinuity is broken, to be renewed again an instant after ; and thus a 



