1902 - 3 .] Mr Manley on Electrical Conductivity of Sea- Water. 361 
coefficient of a water, and accordingly obtains his data from the 
resistance measurements made at two temperatures only. Now, 
the physicist learns from his daily experience in such matters that 
straight line equations are not in the habit of appearing upon the 
scene of his labours with that unfailing regularity for which he 
could sometimes wish ; and even on the rare occasions when such 
an one does present itself, it is generally viewed with much 
suspicion, and is subjected to such rigorous treatment by the 
mathematician that it is speedily robbed of its more primitive form. 
But from this digression we hasten to a further brief consideration 
of the facts contained in Table II. 
On reviewing the data contained in the columns a and /3, one 
is quickly convinced that the assumption made by Knudsen 
would be wholly inadmissible here, for in every case it is obvious 
that the equation obtained is that for some distinctly curved 
line. Hence it follows that variations in the temperature and 
specific conductivity of a water are not always directly pro- 
portional to each other. 
Some further Experiments and Results. 
The conclusions drawn from the data obtained for the water 
collected at Sandown were confirmed by the results obtained from 
an examination of samples of water from two other localities. 
For these I am indebted to the kindness of the Director of the 
Marine Biological Laboratory at Plymouth and to Mr H. E. 
W. Phillips. The sample procured by the former was collected 
midway between Stoke Point and Bolt Tail, and the second 
sample came from about one mile off the shore of Cardigan Bay. 
The Plymouth water was first examined in its natural state, 
and afterwards five samples of very slightly different strengths 
were prepared from it by adding successive portions of 1 gram 
of re-distilled water to 1000 grams of the sea- water. Two 
additional and considerably weaker samples were also prepared by 
mixing 50 and 100 grams of distilled water respectively with two 
3 000-gram samples of sea- water. In Table III. the prepared waters 
are numbered from 1 to 7 in the order of decreasing total salinity. 
The symbols d 24 , p 24 , etc., which appear at the heads of the 
columns, have the several meanings ascribed to them on page 360. 
PROC. ROY. SOC. EDIN.— VOL. XXIV. 24 
