20 
MINUTES OF PROCEEDINGS OF 
for releasing the weight, and wires leading from the gun attached to the 
binding screw in connection with it. 
Everything being now in readiness, carefully level the instrument, and 
suspend the weight. On the gun being fired (or before, if necessary), the 
magnet releases the weight, which in falling registers the screens, as before 
described. As it reaches the bed of the instrument, the steel arms enter the 
Y springs, and gradually bring it to rest. 
The cylinders are capable of registering from twelve to fourteen 
experiments each, after which the paper can be taken off, and preserved for 
reference by applying varnish at the back. 
Eor releasing the weight when experimenting with a carbine, I have found 
the following simple device act perfectly. AB , (Eig. 9) is a piece of ebonite, 
Fig. 9. 
S 
D 
F 
to which is attached a brass spring {CD). FF is another slightly weaker 
spring, insulated from the former, and to which a crutch (G) is soldered, to fit 
the trigger. These are put in connection with the wires from the electro¬ 
magnet. On taking aim, and pressing the finger against B, the springs 
come in contact, releasing the weight; on the pressure being continued, the 
trigger is moved, and the carbine fired. 
By altering the rate at which the finger sets the trigger in action, the first 
registration may be made to take place at any part of the scale. With a 
fixed object, such as a gun, this becomes still more simple. 
Applications of the Instrument. 
An important application of the instrument would be the accurate 
determination of the rate of revolution of rapidly revolving discs or cylinders. 
Thus, for example, suppose the right cylinder of the machine is to be set in 
rapid rotation, and its rate required. All that would be necessary would be 
to drill a small hole close to the bottom of the cylinder, and insert a piece of 
ivory; by fixing a light spring to press against the cylinder, the electrical 
communication would be complete, except at this point. If now the primary 
current be so arranged as to pass from the coil, through the spring and right 
cylinder, back to the coil, it is evident that an induced current would be 
generated each time the cylinder revolved and brought the ivory point under 
the spring, intercepting the current. The secondary wires being attached, as 
before described, a spark would pass from one cylinder to the other through 
the suspended weight; and if the cylinder was put in rapid revolution, and 
the weight released, a row of sparks would indicate the rate; the distance 
between any consecutive two, as measured on the velocity scale, being the 
time taken for one revolution. Similarly, by placing two ivory points 
equidistant from one another, two rows of spots would mark the rate of each 
