158 
TOPULAR SCIENCE REVIEW. 
base, m, and for convenience a column, n, and stand, o, of any 
suitable character, may be employed. Most of the other figures 
are in the form of diagrams, to more clearly represent the elec- 
trical connections. I remark that it is preferable to have the 
light within a case or globe, and that various materials may be 
employed, such as alum-water, between concentric cylinders, to 
lessen radiation, retain the heat, and lessen the electric energy 
required ; or coloured or opalescent glass, or solutions that 
reduce the refrangibility of the light, such as sulphate of quinine, 
may be employed to moderate the light, and the light may 
either be in the atmosphere or in a vacuum. The materials 
that I have found especially adapted to use as light-giving sub- 
stances are set forth hereafter. The electric circuit, fig. 2, 
passes by line 1 to the post r, and by a wire to the lever /, thence 
by the wire or rod k , cap l , wire e, to the post c, through the 
double spiral, a, to the post 6, and by a metallic connection or 
wire to the post n\ and line 4, and so on through the electric 
circuit, and the light be developed in a. The rod k will expand 
in proportion to the heat of the coil, or in proportion to the heat 
developed by the passage of the current through the fine wire k ; 
and, if the heat becomes dangerously high, injury to the appa- 
ratus is prevented by the expansion of rod k moving the lever /, 
to close the circuit at i, and short circuit or shunt a portion of 
the current from the coil a, and reducing its temperature. This 
operation is automatic, and forms the principal feature of my 
invention, because it effectually preserves the apparatus from 
injury. The current need not pass through the wire or rod 7c, 
as the expansion thereof by the radiated heat from the coil a 
will operate the lever /, as indicated in fig. 3, but the move- 
ment is not so prompt. It is to be understood that in all cases 
the action of the short circuit or shunt is momentarily to lessen 
the current through the light-giving substance, and the circuit- 
closing devices play up and down at the contact point, main- 
taining uniformity of brilliancy of light.” 
The use of incandescent substances for producing the electric 
light was patented as far back as 1841. The contrivance for 
preventing fusion or softening is neat and ingenious, but far too 
delicate for the rough purposes of ordinary illumination. Cer- 
tain appendices to the principal claim, in the form of secondary 
batteries, hardly require detailed notice, as not touching the 
main subject of the patent. The ultimate claims may be re- 
duced to the following : — ( 1 ) The combination with an electric 
light of a thermal circuit-regulator, to lessen the electric action 
in the light when the maximum intensity has been attained. 
(2) The combination with the electric light of a circuit-closing 
lever, operated by heat from the electric current or from the 
light, and a shunt or short circuit to divert the current, or a 
