1902-3.] Mr Manley on Electrical Conductivity of Sea- Water. 347 
The Electric Conductivities and Relative Densities of 
certain Samples of Sea-Water. By J. J. Manley, 
Daubeny Curator, Magdalen College, Oxford. Communicated 
by Sir John Murray, K.C.B. 
(Read November 3, 1902.) 
Introductory. 
Several years ago, Dr Yeley and myself were engaged in 
making a prolonged series of measurements of the electric con- 
ductivities of nitric acid solutions of various strengths. During 
the course of the work we were repeatedly impressed by the 
fact that a very slight variation in the strength of a solution 
produced a very marked change in the value of the electric 
resistance, as measured in a somewhat high resistance cell. 
Some little time after the work upon nitric acid had been 
completed, the refractive indices of some samples of sea-water 
were determined ; and it was shewn in a paper * communicated to 
the Society that the optical method for distinguishing between 
the various samples was quite as delicate and as reliable as the 
relative density method. 
By the experience gained during the work upon the nitric acid 
solutions, the present author was led to conclude that the electric 
conductivities of different samples of sea-water would, in all 
probability, vary much more than either the corresponding 
refractive indices or relative densities. Accordingly, it was 
determined to make and compare a series of measurements both of 
the electric conductivities and relative densities of a few samples of 
sea-water, and to establish if possible some simple relationship 
between the two. With this object in view, a bottle of water was 
collected from off the head of the pier at Sandown, I.W., at 8.30 
p.m. on Sept. 8th, 1900. The tide at the time was an inflowing 
one, and at almost half the full height. Before collecting the 
sample, the bottle was thoroughly washed out several times with 
* Proc. Roy. Soc. Edin., Jan. 1900. 
