200 
satisfy. The common increment is 8 c m. The columns 
were made 7 and 9 3 c.m. long. The tints seemed to 
correspond. The columns were made 10 and 12’3 c.m. 
long. The tints again seemed to correspond. The columns 
were made 13 and 15*3 c.m. long. The tints seemed 
again to correspond. Finally, the columns were made 
16 and 18 -3 c.m. long. The tints again corresponded. 
In the two last experiments the greys obtained were 
very deep. I also made the following experiment. I 
took two grey tints : one consisted of 10 grms. BaS04 
and 0'042 grins, of lamp-black. The other consisted 
of 10 grms. BaS04 and 0*4003 grms. of lamp-black. These 
greys were made into a paint by the addition of a little 
water, and pieces of cardboard covered with them. They 
were then dried. These we may denote by and W/3. I 
looked at W/3 through a column 4*1 c.m. long, and 
endeavoured to get a similar tint with W« under the other 
cylinder. For the upper limit the column was 6*95 c.m. 
long, and for the lower limit 6'2 c.m. long. The mean is 
6*57 c.m. I next altered the length of the column over W/3 
to 11-75. In the other cylinder for the upper limit the 
column was 14-9 c.m., and for the lower limit 14-8. The 
mean is 14-85. Hence we have 
By cross multiplication and elimination of W/j 
Theory requires the sums of the indices to be equal. 
The sum on the right hand is 18*32, and on the left 18*95. 
The difference is, I think, not greater than what might be 
due to errors of observation. 
“Results of Observations of the Variable Star T Aquilse,” 
by Joseph Baxendell, F.B.A.S. 
A notice of the discovery of the variability of this star 
