June 8, 1906.] 



SCIENCE. 



879 



P is attached. P fits in a slot in a movable 

 horizontal bar 8, to -which is rigidly attached 

 the Tertieal rod R. The latter slides up and 

 down inside a slotted tube U (Fig. 2), so that 

 the vertical component of the motion of P is 

 transmitted to a pencil mounted on B at T. 

 A large gear wheel G mounted on the shaft 

 (Fig. 2) engages in a rack on the under 



A. If the pin P is set so as to lie in the axis 

 Q, around which B rotates, the fundamental 

 curve of amplitude OQ will be traced. For 

 any ether position of P, the second, third or 

 fifth harmonic, of amplitude PQ, is super- 

 posed upon the fundamental curve. When 

 the disc B is shifted so as to make the dis- 

 tance OQ equal to zero, the harmonic alone is 



edge of a vertical board, 66 x 31 cm., to which 

 a sheet of paper is fastened. When the shaft 

 is turned by means of a crank, the board is 

 advanced horizontally between wooden guides 

 and the pencil T traces a curve, whose form 

 depends upon the setting of the discs A and B. 

 By means of gearing to be described pres- 

 ently, the disc B can be made to rotate either 

 two, three or five times for each revolution of 



drawn. Any phase relation can be produced 

 between the fundamental curve and its har- 

 monic. 



Fig. 1 shows the train of gear wheels that 

 rotate the disc B. a represents a stationary 

 two-inch (5.08 cm. diameter) gear wheel 

 screwed to the bearing through which the 

 shaft passes. The teeth of this wheel en- 

 gage those of a second gear wheel h of the 



