1899-1900.] Mr J. J. Manley on Examination of Sea- Water. 43 
Table G. 
Water. 
Relative 
Deviations. 
Diffs. 
Relative 
Densities. 
Diffs. 
Refractive 
Indices, /x. 
l v 
5 V 
2 V 
4 V 
3 V 
1.02054 
41 
28 
27 
17 
} *00013 
| -00013 
| *00001 
| *00010 
1*02582 
79 
51 
50 
43 
| *00003 
| *00028 
| -00001 
| *00007 
1*33882 
78 
75 
75 
71 
Mean Diff. = *00009 
Mean Diff. = *00010 
The costliness of the refractometer which has been employed 
for the measurements detailed above, might possibly incline an 
individual observer to choose the usual specific gravity method 
rather than the one advocated here ; but where a large number of 
samples of water have to be examined (as, for instance, in a central 
laboratory), the optical method would undoubtedly prove to be 
the most economical and convenient one, on account of the rapidity 
with which the determinations could be effected. 
The author hopes that in a future communication he may be 
able to give an account of some further investigations which he 
intends to carry out with a special form of refractometer, which 
has been designed for studying the changes which the refractive 
indices of liquids undergo with change of temperature. 
