1899-1900.] Mr J. J. Manley on Examination of Sea- Water. 39 
perature ; for this purpose, the waters denoted by l v and 5 V were 
selected. The water having been introduced into the prism, the 
minimum deviation for the D line was found in the manner already 
described; the thermometer was then removed, and the aperture 
in the prism closed with a stopper. A Bunsen burner was then lit 
in the closed room, in order to raise the temperature ; after a time, 
the minimum deviation was again determined, the process being 
repeated for two other and still higher temperatures. In this 
manner were obtained the minimum deviations at four different 
temperatures, as shown in Table C. 
Table C. Water l v . 
Temp, at which the min. \ 
a. 
b. 
c. 
d. 
dev. was taken. / 
20° -0 C. 
22°'9 C. 
23° -9 C. 
2 4° *9 C. 
Minimum deviation in \ 
86,884" 
86,796" 
86,766" 
86,732" 
secs, of arc. J 
The data given in the above table enable us to determine the 
value of a correcting factor, which may then he used to reduce all 
observed minimum deviations to a common temperature. In the 
fourth column of Table D, the values deduced for the factor are 
shown; it will he seen that the mean value is 31". 
Table D. 
Temp. diff. 
Diff. in dev. 
Diff. in the 
min. dev. for 1° C. 
From experiments a and b 
2°*9 C. 
88" 
30" -3 
,, ,, a and c 
3 0, 9 ,, 
118" 
30" *2 
, , , , a and d 
4°°9 ,, 
152" 
31"-0 
,, ,, b and c 
l°-0 ,, 
30" 
30"'0 
,, ,, b and d 
2°'0 ,, 
64" 
32" -0 
’ ,, ,, c and d 
l°-0 ,, 
34" 
34" *0 
Mean = 31". 
Similar measurements applied to the water marked 5 V led to 
exactly the same value for the correcting factor. Since the waters 
differ hut slightly from each other, it may he assumed, without the 
