1876.] 
377 
at South Kensington . 
In the department of Physics we find : — 
Original apparatus with which Faraday obtained the 
magneto-eleCtric spark. — A welded ring of soft iron, 6 inches 
in diameter, 7-8ths of an inch thick, one part covered by a 
helix A containing about 70 feet of insulated copper-wire, 
occupying about 9 inches in length upon the ring. The 
other part covered by a second helix B containing about 
60 feet of insulated copper-wire. The helices are separated 
from each other at their extremities by ^ an inch of the un- 
covered iron. The iron ring was converted into a magnet 
by passing a voltaic current through the helix A. This in- 
duced an electric current in the helix B, and a small spark 
was for a moment seen at the carbon terminals. 
Faraday’s original apparatus for magneto-eleCtric induc- 
tion by a permanent magnet. — A pasteboard tube is sur- 
rounded by a helix C of insulated copper-wire. The diameter 
of the tube allows a cylindrical bar magnet to pass freely 
into it. The terminal wires of the helix are connected with 
a galvanometer. On the introduction of a permanent bar 
magnet into the helix, and on its withdrawal from it, cur- 
rents of electricity were induced in the helix which caused 
a deflection of the galvanometer needle. 
Faraday’s rotating rectangle, for illustrating the induCtive 
aCtion of the earth. — The wire rectangle provided with a 
commutator for collecting the currents was attached to a 
galvanometer, and rotated in the line of the magnetic meri- 
dian, the eleCtric current induced in the reCtangle deflecting 
the galvanometer needle. 
Various helices, spirals, &c., used by Faraday in his re- 
searches on magneto-eleCtric induction, &c. 
A magnet made by static electricity, with note by Fara- 
day. — “ A magnet made at the Royal Institution by an 
eleCtric discharge from 70 square feet of charged surface. 
Present, Sir H. Davy, Pepys Jordan, Bostock, and 
Faraday.” 
Portion of the battery used by Sir Humphry Davy in de- 
composing the alkalies. * 
Diagrams of magnetic curves, prepared by Faraday. 
Coils and helices, used by Faraday in his eleCtro-magnetic 
researches. 
Model frequently used by Faraday during his researches 
on the rotation of a ray of polarised light by electricity and 
magnetism. 
Block of glass pierced by sparks from an induCtion-coil. 
Presented to Faraday by M. Ruhmkorff, 1861. 
