292 THE ROYAL SOCIETY OF CANADA 



calibration curve was plotted and thence a table constructed, giving 

 the wave-length for each . 1 of the comparator scale with differences 

 for the second decimal place. The dispersion of the spectragraph 

 was such as to require about . 05 at the violet end and . 01 at the red 

 end for one Angstrom unit. 



McMaster University, 



Toronto, Canada. 



May 1, 1922. 



