878 



SCIENCE. 



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



adapted for this purpose, and might perhaps 

 also be employed to advantage in illustrating 

 some of the wave-forms that occur in other 

 branches of physics. It does not compound 

 simultaneously a large number of curves of 



harmonic, and can be quickly adjusted to give 

 any desired amplitude and phase relation. 

 The curves are large enough to be seen dis- 

 tinctly from all parts of a good-sized lecture 

 room. The whole instrument is very compact 



difierent periods, as does the machine of and easily portable. Much praise is due to i 



Mach," Michelson's harmonic analyzer,^ or the 

 arrangement recently devised by Lord Ray- 

 leigh for illustrating the nature of white 

 light.' It is, however, capable of drawing 

 accurately the resultant of a fundamental sine 

 curve and either its second, third or fifth 



'Pogg. Ann., 129, p. 464, 1866. 



° A' brief description of the harmonic analyzer 

 is given in Michelson's ' Light Waves and their 

 Uses.' 



*PMl. Mag., 11, p. 127, January, 1906. 



Mr. F. H. J. Newton, the college mechanician, 

 for the skill with which he has carried out the 

 details of construction. 



rig. 1 shows front and side elevations of 

 the instrument, somewhat simplified for clear- 

 ness. Fig. 2 is from a photograph of the 

 entire instrximent. The lettering is identical 

 in both figures. 



A hard rubber disc A 21 cm. in diameter, 

 mounted at the end of a horizontal shaft, 

 carries a smaller disc B, to which a short pin 



