880 



SCIENCE. 



[N. S. Vol. XXIII. No. 597. 



same size, which is rigidly attached to a short 

 shaft M passing through the disc A. At the 

 other side of A are mounted side by side on 

 this shaft three gear wheels, of pitch diameters 

 7.62, 8.12 and 8.71 cm., respectively. These 

 engage three smaller wheels, of diameters 2.54, 

 2.03 and 1.45 cm., which are mounted loosely 

 on the shaft Q of the disc B. A pin G fitting 

 in a longitudinal slot cut in this shaft can be 

 thrust in or pulled out, so as to lock any one 



OQ any desired value from zero to twice OM. 

 NN is clamped to the brass plate F, which is 

 screwed to the disc A and is so shaped as to 

 bridge over the gear wheels, bringing the axis 

 of NN in line with the axis M. The plate F 

 is partly visible in Fig. 2. It will be noticed 

 that the sizes of the three concentric gears on 

 shaft Q, and of the three corresponding gears 

 on shaft M, are such that MQ is 5.08 cm., 

 the same as OM. The period of the funda- 



of Ihe three small gears on to the shaft. In 

 the front elevation (Fig. 1) only one of the 

 three pairs of gears is represented. When the 

 disc A is rotated, the gear b rolls around on a, 

 and, as is seen from the relative diameters of 

 the two sets of gears mentioned above, the 

 disc B is caused to rotate two, three or five 

 times for each turn of A, according to the 

 setting of pin C. 



The shaft Q is carried by the arm NN, 

 which can be swung around M as a. center 

 and clamped so as to give to the distance 



mental curve is represented by a distance of 

 48 cm. on the paper. 



The pin P, instead of being attached di- 

 rectly to the disc B, is held by a small brass 

 block that slides in a groove on the bridge E 

 which spans the disc. Space is left below this 

 bridge for the pin that locks the gears on 

 shaft Q, and the pin P can readily be clamped 

 so as to give to the harmonic wave any ampli- 

 tude up to 8 cm. The bridge is provided with 

 a set of graduations. To adjust the phase of 

 the harmonic, it is only necessary to loosen 



