432 



r x+^ 



J 



i ^ 'y*~ 



(U, , A ... 



/ r O 1 2 

 V* > * J * 



1 



=D 



COS 



sin 



, [cos] 

 = 1 to;' =7, [cos], [sin], [cossiri] 



all the developments being carried up to e 7 , the limit of the for- 

 mulae from which they are deduced. 



IV. " On the Application of Electrical Discharges from the In- 

 duction Coil to the purposes of Illumination." By J. P. 

 GASSIOT, Esq., F.R.S. Received March 29, 1860. 



The subjoined figure represents a carbonic 

 acid vacuum-tube of about ^ of an inch inter 

 nal diameter, wound in the form of a flattened 

 spiral. The wider ends of the tube, in which 

 the platinum wires are sealed, are 2 inches in 

 length and about ^ an inch in diameter, and 

 are shown by the dotted lines ; they are enclosed 

 in a wooden case (indicated by the surrounding 

 entire line), so as to permit only the spiral to be 

 exposed. 



When the discharge from a RuhmkorfFs in- 

 duction apparatus is passed through the vacuum- 

 tube, the spiral becomes intensely luminous, ex- 

 hibiting a brilliant white light. Mr. Gassiot, 

 who exhibited the experiment at the meeting 

 of the Society, caused the discharge from the 

 induction coil to pass through two miles of cop- 

 per wire ; with the same coil excited so as to give a spark through air 

 of one inch in length, he ascertained that the luminosity in the spiral 

 was not reduced when the discharge passed through 14 miles of 

 No. 32 copper wire. 



