28 
POPULAR SCIENCE REVIEW. 
For the convenience of M. Jablochkoff, Gramme has lately 
devised a similar instrument to that described above, except 
that the revolving drum has eight flat bars of iron wound 
lengthwise with wire placed radially, and supplied with a con- 
tinuous current from Gramme’s original generator. External 
and concentric to these are thirty-two coils, forming one or more 
alternating circuits at will. They are, in practice, coupled 
together so as to produce four. The intensity of the machine 
is that of 16,000 candles. As applied to lighting the Avenue 
de l’Opera at Paris, by means of sixteen Jablochkoff candles, it 
is driven at the rate of 600 revolutions per minute, and is said 
to require an engine of 16-horse power. 
Improved methods for the production of the current are far 
more recent than those adapted for its exhibition. Indeed, a 
mechanical lamp, hardly, if at all, inferior to those lately 
patented, dates back as far as April 1855. The specification 
of Mr. Henry Chapman, sealed on June 12th in that year, is 
before us, under the title of 66 An Improved Electro-mechanical 
Apparatus for Supplying and Adjusting the Electrodes used in 
the Production of the Electric Light.” It works entirely by 
means of gravity, and dispenses with the costly and easily 
deranged clockwork of the Serrin, Foucault, and Siemens * lamps, 
which are all fitter for the physical laboratory than for general 
purposes. The comparative forgetfulness into which this excel- 
lent contrivance (see Plate II.) has fallen is probably due to the 
failure of the Electric Light and Colour Company which adopted 
it, and which proposed to compensate for the expense of the bat- 
tery by producing salts of tin, and other metals useful in dyeing. 
In its day it was highly successful, and was proposed for use in 
reconnoitring the enemy’s positions during the Crimean war. 
Mr. Browning has long advertised several lamps acting on 
this simple but effective method, although he is entirely antici- 
* In the Siemens automatic electric lamp the carbons are held vertically 
one over the other in the same relative position as in the Serrin lamp. In- 
side the lamp is a train of wheels gearing into racks formed, one on the 
stem of the lower and the other on the stem of the upper carbon holder. 
These wheels are so arranged that, assisted by gravity in the upper carbon 
holder, which is made sufficiently heavy, the points of the two carbons are 
caused to remain a precise and defined distance apart, which distance is con- 
stant during burning, and by means of which the shortening of the carbons 
by combustion is regularly followed up. A vane regulator or fly is used to 
control the rate of descent of the upper carbon and the corresponding ascent 
of the lower one. Should the carbons approach too closely they are 
separated by means of an electro-magnet which acts upon the end of an 
oscillating lever, which, during its periods of oscillation, causes the train of 
wheelwork to revolve in an opposite direction, and so to separate the carbons 
and to restore the voltaic arc. 
