136 Proceedings of the Royal Society of Edinburgh. [Sess. 
avoidable experimental error rather than to the fact that the densities 
were determined at very different temperatures. During this present 
investigation the temperature ranged in value from 16° C. in the English 
Channel to 30° C. in the Red Sea. 
All the samples of water examined were taken from the surface at 
the bow of the ship ; and a sample was collected every four hours during 
the voyage. In Table II., above, are given the latitude and longitude of the 
spots whence the waters were obtained, the date and hour of the day, and, 
in most cases, the temperature of the water at the time of collecting. The 
specific gravities of the 115 sea-water samples taken aboard, are set forth 
in column 7 in the table ; and in the last column are indicated the localities 
in which the actual specific gravity measurements were made. 
Throughout Table II. the “ specific gravity ” may be taken to mean 
the ratio between the densities of the sea-water and air-free distilled water , 
both at 18° G. 
The variations in the density of the sea-water at the surface and along 
the ship’s track are most conveniently shown according to the plan pur- 
sued in the “ Challenger ” Reports. They are therefore plotted graphically 
in fig. 4. 
In conclusion, I wish to thank Mr J. J. Manley for much practical 
assistance given in Oxford ; Dr H. B. Baker ; the Government Grant 
Committee of the Royal Society for a grant to cover the cost of the 
reading microscope ; and Mr M. J. Sarson, second officer of the Oruba, for 
his kindness in furnishing me from time to time with the ship’s bearings. 
Trinity College, 
Kandy, Ceylon. 
{Issued separately April 19, 1913.) 
