62 THE ROYAL SOCIETY OF CANADA 
able for measurement. Similarly in the À 4250 region besides the 10 
lines selected for measurement by the committee 5 other lines, embrac- 
ing those found by Adams to give systematic deviations were included. 
30. The following table contains the mean residuals in metres 
per second grouped according to latitude, obtained from Plaskett’s 
measures of about 14 plates and from DeLury’s measures of 16 plates 
at 45600. The first three columns contain the wave-length and the 
source and intensity of the lines measured. The next seven columns 
contain the mean residuals, taking account of the signs, at the seven 
different latitudes observed. Each of these is the mean of the residuals 
from 14 or 16 plates. The separate residuals are not given on account 
of the space that would be required. The last column but one is the 
mean of all the residuals without regard to sign or the average residual, 
while in the last column the sign is taken into account, and we have the 
mean algebraic residual. At the foot of the columns the mean probable 
errors of measurement of a single line at each latitude are given. 
