44 Proceedings of the Royal Society 
the rigorous zigzag system of titration adopted. This will be 
done in future. 
A great many determinations of the chlorine, or rather total 
halogen, present in the samples of sea water were made, but, from 
various causes, the probable error of each experiment was so large 
as to render the results useless for the purpose of detecting the 
difference between the ratio of salinity to density in estuary water 
and in ocean water. Tor this reason the figures are not published. 
The density of the water may be taken as an index of its 
salinity, although there are no data available for interpreting each 
density into its corresponding percentage of total salts. This can 
only be done in the case of ocean water proper, for which tables 
have been constructed by several chemists.* 
II. Results of Preliminary Work. 
1. Notes of Previous Work 
In 1816 Dr John Murray read a paper to this Society “ On the 
Composition of Sea Water,” the samples which he analysed being 
taken from the Firth of Forth near Leith. The paper (Trans. 
Roy. Soc. Ed in. for 1816) contains results of great theoretical 
value, which were instrumental in modifying the theory of the 
existence of salts of different bases and acids in solution, and 
which altogether changed the mode of analysis of sea and mineral 
waters. Attention was given more particularly to the solid 
constituents, and no observations seem to have been made by Dr 
Murray on the variations in salinity at different parts of the firth. 
Dr John Davy published a paperf in 1843, “ On the Temperature 
and Specific Gravity of the Water of the Firth of Forth.” He 
examined the temperature and density of the water at the end of 
Leith Pier on eight occasions, at intervals of about a month. His 
entire observations are reproduced in table (V.). 
It was Davy’s intention to continue the monthly observations for 
a number of years, but he had to leave Edinburgh, and they were 
stopped. Since no particulars as to how the densities were 
* See Dittmar, Phys. Chem. Chall. Pep., I. pt. i. 1884. 
t Ed. New Phil. Journ., xxxvi. p. l.fj 
