ON A NEW VELOCITY RECORDER. 285 



on the tripping lever I J. When the clock allows the lever I J 

 to fall the detent is released, the snail K makes a nearly complete 

 revolution and comes to rest with its point holding up the lever 

 V W, so that the friction roller Q is out of contact with the sector 

 N, and then the pen falls to zero. As soon as the notch I in the 

 scape-cam lifts the tripping lever, the snail completes its revolu- 

 tion and the roller Q again takes hold and begins to lift the pen. 



On each of the time arbors C, D, E, F, is a notched wheel or 

 cam (shown shaded), all the cams being arranged in one plane, 

 and close alongside is the tripping lever I J, so that by removing 

 or placing certain pins opposite each cam its time of falling may 

 take place regularly at the period of one revolution of any of the 

 time arbors. The lifting of the striking lever however, must be 

 done by the quickest moving cam, viz., that on the scape arbor, 

 so that the pause during which the pen is uncoupled may be 

 reduced in duration. Hence a fairly heavy balance is needed to 

 control the very strong mainspring required to do the work of 

 lifting the striking lever. The cam plates should be fixed on 

 friction collets so that they may be easily adjusted to any altera- 

 tion of the clock dial, and to ensure that the notches come opposite 

 the pins in the tripping lever I J at the proper times. This 

 tripping lever is close inside the back plate and all or any of the 

 pins may be unscrewed from the back to alter the differenting 

 period to suit the particular experiment in hand. 



The intermittent motion is transmitted to the drum by bevils 

 on the arbor G, which are so geared that the drum moves one 

 revolution for six turns of G, and for three hundred and sixty of 

 K ; thus as the circumference of the drum is about eight inches, 

 there will be about forty-five lines per inch, and an octavo-sheet 

 will contain a record lasting from one hour to fifteen days, 

 according as the lever I J is allowed to drop at the time intervals 

 corresponding to the arbors F, E, D, or C of ten seconds, one 

 minute, seven and a half minutes or one hour. 



The length of the line drawn by the pen being dependent solely 

 on the number of revolutions of the shaft T S, it is convenient to 



