48 DR. JAMES BOTTOMLEY^S 



Now pour out from a until the colour seems tlie same as 

 in (8 ; before reaching the theoretical division sight will fail 

 to discern any difference of colour. Now, if we proceed 

 cautiously, as we approach the limit there will be a natural 

 hesitation and tendency to stop ; and it seems likely that in 

 most cases, in obedience to that feeling, we shall stop with 

 a column a little too long. Now suppose we start with the 

 cylinder a empty and pour fluid into it ; as we again ap- 

 proach the limit cautiously we shall again have a tendency 

 to stop, and, inasmuch as before reaching the limit we pass 

 through tints which we cannot distinguish from it, we are 

 likely to take a column of fluid too short. In my own 

 case I have noticed this on several occasions. For example, 

 in trying to estimate a particular colour, the mean of seven 

 trials made by pouring out from the cylinder gave 14* i as 

 the length of the column, the mean of seven trials made by 

 pouring into the cylinder gave 13*7 as the length; and with 

 disks inside, the mean of six trials made by moving the disk 

 from below upwards gave 12*5 as the length of column, 

 while moving from above downwards the mean of six ex- 

 periments gave 1 1 '7. In trying to estimate a colour, it 

 seems to me that it would be well to approach the limit by 

 both ways, and then take the mean of the results. 



In a previous part of this paper I stated that altering 

 the position of the cylinders made a little difference in my 

 perception of colour. I made some experiments to try 

 this. I took a solution containing 2400, and poured from 

 the cylinder on the right hand into the cylinder on tlie left 

 hand; the columns ought to be equal. The mean of nine 

 trials gave length of column on right hand 11 -2, length of 

 column on left hand io'6i. In these experiments the 

 judgment was made using both eyes. I next tried using 

 one eye only. With the right eye the results were, length 

 of column on right hand io-86, length of column on left 



