C. A. Young on a proposed Printing Chronograph. 108 
forming a fork ; at the other end it has a little projection (2). 
The arm // is delicately pivoted at (x), and at the other extremity 
passing freely between the pins of the fork (y) carries the steel 
pind. Atthe middle it is expanded into a ring, gg, through 
which the arbor B passes without touching: ff is made of soft 
iron, and the annular expansion at the middle thus serves for 
the armature of the electro-magnet whose action is to produce 
the desired result at the touch of the observer's key. 
A light spring between e and f solicits f to the left, and thus 
whenever the electro-magnet is not acting keeps the pin d in 
the position represented in fig. 2, engaged with the arm b. In 
this state of things the type-wheel ¢¢ will be carried round con- 
tinuously by A. Of course the arms e and f must be as light as 
consistent with sufficient stiffness, and their weight must bal- 
ance in all parts of the revolution, and neither tend to accelerate 
or retard the motion of the type-wheel. 
Close behind the arms e and / is placed a stationary dise of 
metal, H H, having one hundred equidistant holes pierced in it 
in a circle, so situated that whenever the arm / is drawn to the 
right by the magnet (thus disengaging the type-wheel from the 
train) the pin d will immediately enter one of these holes, stop 
the type-wheel, and hold it in place until the magnet ceases to act. 
his magnet is peculiar in having for its core, instead of a 
solid rod, an iron tube, through which the axis B passes. Thus 
the pole of the magnet is always in the same position with ref- 
erence to the armature gg, notwithstanding its revolution. As 
only one pole of the magnet acts upon the armature it is neces- 
sary to make the coils more powerful than ordinary. 
| or bringing the hammer down upon the paper and movin 
the paper along after each impression any one of many different 
plans might be used. Probably the best, leaving expense out 
of the account, would be to have the hammer raised by an inde- 
pendent train of wheelwork, which should be unlocked by an 
electro-magnet at the instant of observation, thus releasing the 
ammer, and allowing the wheelwork after the blow to move far 
enough to raise the hammer again, and carry the paper forward, 
nother more simple plan is to work the hammer directly by 
& powerful electro-magnet, to which the magnet Z should act as 
a relay—that is, whenever the pin d touches the disc H it should 
establish a current which should bring down the hammer upon 
the paper; the hammer in rising after the blow carries the paper 
along one space. 
rovision is also made for carrying the paper along several 
Spaces at the will of the observer, so as to leave an interval be- 
tween the record of different stars. 
Although there are only fifty numbers on the type-wheel_ 
which prints the decimal of the second, the record is made to 
the nearest hundredth. There being one hundred holes in the 
od 
“e 
