21 
Very little hydrographical work seems to have been done 
in the Irish Sea, though the Clyde sea-area immediately to 
the north of it has received much attention ; in fact almost 
the only analyses of the water seem to be those done by 
Thorpe and Morton in 1870 (J. C. 8. xxiv. p. 506), so there 
is little past work to comment on. 
The working here described has been done mainly by the 
methods employed by Dittmar, Knudsen, Jacobson, &c., and 
the working out of many of the results has been performed 
with the assistance of Knudsen’s Hydrographical Tables. 
The values obtained are given in considerable detail, 
which it is hoped may be of some value as showing the 
degree of accuracy obtained by different methods. 
1.—CoLLECTION OF THE SPECIMENS. 
These were obtained mainly from the Biological Stations 
and from our fisheries steamer, but not on any regular ex- 
pedition. For this reason I have not yet been able to obtain 
specimens from several desirable places, nor to obtain in all 
cases the temperature of the water at the time of collection ; 
further, the specimens are all of surface water, as a Mill’s 
water bottle which was ordered did not arrive early enough 
to be of use. I hope to use it in a further investigation on 
a future occasion. The samples consisted each of about a 
litre and a half of water, and were kept in glass bottles with 
ground glass stoppers till used in the laboratory. This 
method has the disadvantage of slightly increasing the 
alkalinity owing to the action of the water on the glass, but 
this increase is probably very slight since it was seldom 
that the water was kept more than two or three days before 
being used for the determination of this character. 
