SEA-FISHERIES LABORATORY. 129 



Very little hydrographical work seems to have been clone 

 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. S. 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. 



