zSyS.] The Phonograph. 251 
recently Mr. Edison has made records on copper-foil that 
could be read at a distance of 275 feet in the open air. 
Fig. 4 is a view of a very beautifully arranged instrument, 
designed and constructed for his own use and instruction, 
by Mr. Augustus Stroh. 
The cylinder is driven round at a surface speed of about 
1 foot in a second, by means of exceedingly simple controlled 
clockwork mechanism actuated by a descending weight, at- 
tached, upon Huyghen’s maintaining principle, to an endless 
chain passing over a pulley fixed upon the principal 
axis of the instrument, so that it is possible to wind up 
the weight while the cylinder is rotating without affecting 
' its speed. 
The controlling fan, or governor, which is beautifully 
simple and efficient, consists of two circular disks of brass 
mounted at the upper ends of two light levers, which are 
geared together at their lower ends, so as to cause them to 
fly out symmetrically on each side of the axis of rotation of 
the vertical fly-shaft to which they are pivoted. When the 
machine is started (by taking off the pressure of a small 
cork-lined brake-block, shown in small detail sketch, which 
presses against the cylindrical head of the fly-spindle) the 
disks fly out under the influence of centrifugal force, and the 
resistance of the air to the motion of the spindle is increased 
by the increase in the diameter of their path of rotation if 
the speed become too great. Should, however, the speed of 
rotation tend to fall off, a spiral spring, which can be 
attached to the fan levers at any position in their length, 
draws them together, and, by reducing the circle of their 
path, offers to the mechanism a diminished resistance to 
rotation. 
At a recent meeting of the Society of Telegraph Engineers 
both the instruments which we here describe were exhibited 
in illustration of a very interesting paper, by Mr. W. H. 
Preece, C.E., upon this last and perhaps greatest marvel of 
the application of Science which this or any other age has 
seen. 
Mr. Edison’s first form of phonograph was represented by 
a very successful instrument made by an amateur, Mr. Pigeon, 
from descriptions received from America, and in which the 
two diaphragms, the one of paper and the other of metal, 
were employed. 
The second form of apparatus was represented by Mr. 
Edison’s own instrument (Fig. 1), and the more perfect form 
driven by controlled mechanism was represented by Mr. 
