46 ; Faraday as a Discoverer. 
pulse which vanished immediately. On interrupting the a : 
The magnet, for example, must not be passed quite through 
the coil, but only half through, for if passed wholly through, 
the needle is stopped as by a blow, and then he shows how this 
He next operated with the powerful permanent magnet of the 
Royal Society, and obtained, with it, in an exalted degree, all 
darkest physical phenomena of that day. Arago had discovered 
in 1824, that a disk 
bringing a vibrating magnetic needle sus ended over it rapidly 
to rest ; and that on causing the disk to rotate the magnetic 
was not the slightest measurable attraction or repulsion exerted 
tween the needle and the disk ; still when in motion the disk 
been examined in this 
ined b 
bage and Sir John Herschel ; but it still remained a mystery. 
Faraday always recommended th i j 
