100 C.A. Young ona proposed Printing Chronograph. 
manner practised for some years at the Dudley and other ob- 
servatories. It might perhaps be well to substitute for the half 
seconds pendulum commonly used, a pendulum beating quarter 
seconds, the requisite rapidity of oscillation being secured by a 
or . 
I shall assume then that we have an axis revolving once per 
second with a uniform motion. It is immaterial, of course, 
whether this uniform motion is obtained through the spring- 
governor, or by means of some other of the many ingenious in- 
ventions that have been contrived for the purpose, though I do 
not think any can be found more simple and effective. 
ose now that in fig. 1, A is 
such an axis, and that Bis a sec- 
ond axis mounted on the prolonga- 
tion of A, but entirely separate, 
bearing a type-wheel, ¢¢, at its ex- 
tremity. Suppose also that f is a 
balanced arm attached to the ex- 
tremity of A, and that 0 is a similar 
arm attached to B, and bearing a 
pin, d, which engages with / 
It is then evident that A in its ee 
motion would take along the type- 
oe 
id 
acceleration: 2d, at the instant when the arm / strikes the pin 
it will receive a shock due to the inertia of B and its appendages; 
this would tend to retardation. The difference only of the two 
effects would have to be corrected by the action of the spring- 
governor; and it is believed, if the governor train has consider- 
able momentum, and the type-wheel ¢¢ is made.as light as pos 
sible, that the disturbance will be nearly or quite insensible. _ 
The mechanical arrangements by which this idea i 
