156 
POPULAR SCIENCE REVIEW. 
as the publication of Mr. Edison’s specification. This, trans- 
lated, as is said, from the French, appeared in the “ Standard ” 
of Feb. 10, but was rendered comparatively difficult of compre- 
hension by the absence of the figures and diagrams referred to 
in the text. It was soon followed by a more complete account 
in the “ Engineer ” of Feb. 14, from which, by the courtesy of 
the proprietors, I am enabled to borrow the excellent figures 
illustrating the present paper (Plate V.). These show the three 
principal out of no less than forty-eight drawings lodged with 
the French specification. 
Much of his contrivance is of great ingenuity, and. evidences 
considerable mechanical skill. But all competent authorities 
are agreed in considering that it in no way supersedes existing 
methods, or that it in any sense fulfils the revolutionising prog- 
nostics freely made in its favour. It consists of two parts — 
1, the means of producing electricity ; 2, the lamp. 
The electric-magnetic machine is thus described in the speci- 
fication : — 
66 It has long been known that if two electro-magnets, or an 
electro-magnet and a permanent magnet, be drawn apart or 
caused to pass by each other, electric currents will be set up in 
the helix of the electro-magnet. It has also been known that 
vibrating bodies, such as a tuning-fork or a reed, can be kept in 
vibration by the exercise of but little power. I avail myself of 
these two known forces and combine them in such a manner as to 
obtain a powerful electric current by the expenditure of a small 
mechanical force. In fig. 1 of the drawing a tuning-fork, a 2, is 
represented as firmly attached to a stand, b 2. This fork is pre- 
ferably of two prongs, but only one might be employed, upon the 
principle of a musical reed. The vibrating bar or fork may be 
2 metres long, more or less, and heavy in proportion. It has its 
regular rate of vibration, like a tuning-fork, and the mechanism 
that keeps it in vibration is to move in harmony. A crank and 
revolving shaft, or other suitable mechanism, may be employed, 
but I prefer a small air, gas, or water engine, applied to each end 
of the fork. The cylinder a 1 contains a piston and a rod b 1, 
that is connected to the end of the bar, and steam, gas, water, 
or other fluid under pressure acts within the cylinder, being 
admitted first to one side of the piston and then the other by a 
suitable valve ; the valve and directing rod c 2 are shown for this 
purpose. The bar of fork a 2 may be a permanent magnet or an 
electro-magnet, or else it is provided with permanent or electro- 
magnets. I have shown an electro-magnet, c 1, upon each prong 
of the fork — there may be two or more on each — and opposed to 
these are the cores of the electro-magnets d . Hence as the fork 
is vibrated a current is set up in the helix of each electro- 
magnet d in one direction as the cores approach each other, and 
