THE COLLAPSE OF THE ELECTRIC LIGHT. 
159 
portion thereof, from the light. (3) The combination with the 
electric light of a circuit-closer operated by heat, and serving to 
place more or less resistance in the circuit. (4) The combina- 
tion with an electric light of a diaphragm operated by the 
expansion of a gas or fluid in proportion to the temperature of 
the light. (5) The combination with a vibrating body similar 
to a tuning-fork of mechanism for maintaining the vibration, 
and magnets, cores and helices, whereby a secondary current is 
set up, so as to convert mechanical motion into electric force or 
the reverse. (6) The combination with electric lights of means 
for regulating the electric current in proportion to the heat 
evolved, so as to prevent injury to the apparatus. 
The question, of course, remains whether this, which is the 
only complete statement yet made, contains the whole of what 
Mr. Edison has to divulge. It has been somewhat hastily con- 
cluded that this is the patent on which he depends. But both 
the causes named above may conduce to the keeping back of 
some important matter by way of a surprise. If, however, this 
be his complete utterance, there is ground for the disappoint- 
ment very openly expressed in many quarters. 
It is remarkable that nothing is said about the subdivision of 
the current, one of the points most insisted on in the earlier 
reports of Mr. Edison’s contrivances, nor of the mode of mea- 
suring the current. 
Another recent contrivance for producing light from elec- 
tricity falls into the same category as Mr. Edison’s, owing to its 
depending on the principle of incandescence — viz., the Sawyer- 
Man patent— which deserves brief notice in this place. It is 
produced from a small pencil of carbon placed in a closed cham- 
ber, and separated from the conductors by three diaphragms. 
The conductors are of copper, shaped so as to have great radiating 
surface, and thus to prevent conduction downwards into the 
mechanism of the base. The whole is enclosed in a vessel 
containing nitrogen, with a provision for fixing any residual 
oxygen. The wasting of the carbon by oxidation is thus pre- 
vented. To obviate the danger of crumbling or disintegration 
of the carbon from sudden heating, an ingenious ‘switch,’ or 
current-diverter, is interposed, the mechanism of which is far 
too complicated for description without diagrams. The greater 
part of the light is produced by a small part of the current, and 
in this condition a very small increase materially enlarges the 
incandescence. The wires supplying the electricity may be con- 
veniently run through existing gas-pipes, each lamp being 
supplied with a switch placed in the wall, so that by turning a 
key the light is turned off or on. As long as the house is con- 
nected with the main it makes no difference to the producer 
whether the lights are on or off, since the resistance of the entire 
