DR. JAMES BOTTOMLEY ON COLORIMETRY. 185 



I now made the length of the column over W, 13 centira. 

 The equivalent column over Wj was, as the mean of two 

 trials, 7 '5. Hence 



From these experiments we get as the sum of ^, and t'^ 29*7, 

 and the sura of ^'j and t^ 27*8. 

 A second experiment gave 



Here /, + /!'i = 28-45, and /i + ^', = 2876. 

 A third experiment gave 



Here ^i + ^'2=25*3, and ^'j + Z^ = 24-93. 

 A fourth experiment gave the following results : — 



Here /, + i'j, = 28*4, and ^', + ^j. = 27-4. 

 A fifth experiment gave 



Here we have ^, + ^'1 = 31 '95, and ^', +/z = 30'35. 



It seems to me that the above results arc as favourable 



