324 KNIGHT DUNLAP 



The practical advantages of this kymograph are: 



1. Simplicity of construction. There are few parts, and 

 these are of simple and strong design. 



2. Comparative noiselessness. If desired, the master fork may 

 be placed in another room, or in a sound proof box. The motor 

 itself makes little noise when operated on a fork-interrupted 

 current. Driven by A. C., the noise is a little greater. 



3. Ease of operation. The motor being in continuous rota- 

 tion, the drum may be started and stopped at will, by manipu- 

 lating a switch anywhere in the room or in another room. 



4. Economy of writing surface. Full speed, and complete 

 stop are attained by the drum in a very small fraction of a 

 second, so that the usual waste of surface due to the " picking 

 up" in speed of the usual spring or motor drive is eliminated. 



5. Simplicity of time measurement. The rate of the fork 

 being known, the rate of the drum is known and is invariable. 

 The clutch is so efficient, that in tests which I have made, a 

 fork-tracing taken several times around the drum has given 

 but a single line, the writing point following the same path on 

 the first, second, third, and following tracings. In making this 

 test, a recording fork must be used which is in exact tune 

 (snychronous or even multiple) with the fork driving the motor; 

 or a magnetic recorder may be driven from the same fork. In 

 the latter case there may be slight temporary disturbances of 

 the superposition due to changes in the latency of the magnet, 

 but these may be detected, as may also aberrations due to 

 change in amplitude or in form of the vibration. 



Knowing the rate of the drum, and its diameter, the relation 

 between seconds and millimeters may be established, and hence 

 no time-line on the drum is needed in most cases, since the 

 records may be read by the aid of a millimeter scale. 



