CLYDE SEA AREA. 709 



range of salinity it represents, it is interesting to notice whether position in vertical 

 depth produces any effect. The result — leaving out of account two samples taken from 

 a few fathoms beneath the surface — is as follows : — 







Corresponding 









Chlorine. 



Percentage of 



Sulphuric 



Carbonic 





Normal 



Acid. 



Acid. 







Sea Water. 







4 surface samples, 



. 17-996 



92-5 



0-11725 



0-1483 



3 bottom samples, 



. 18-157 



93-3 



0-11729 



0-1451 



Here we find the amount of sulphuric acid practically the same in both sets, but the 

 alkalinity of the fresher surface water is markedly greater than that of the Salter water 

 from the bottom, thus confirming, in a sufficiently satisfactory way, the deduction from 

 the previous discussion. 



Taking the 116 determinations of sulphuric acid in order of magnitude of the ratio, it 

 is found that of the 58 cases in which the ratio was higher than 0'11740, 26 were surface 

 samples, 28 were bottom samples, and 4 from intermediate depths; while of the 58 cases 

 in which the ratio was lower than 0"11740, two samples were from intermediate depths, 

 and 28 each from surface and bottom. The amount of sulphuric acid would thus appear 

 to be practically independent of depth, and, by implication, independent also of salinity. 



Treating the carbonic acid, or rather the alkalinity, results in the same way, a well- 

 marked concentration of high values amongst surface samples is found, and a still more 

 distinct concentration of low values amongst bottom samples. The 58 alkalinity ratios 

 higher than 0*1464 referred to 31 samples of surface water, 2 from intermediate depths, 

 and 25 from the bottom. The 58 lower than 0*1464 referred to 23 samples of surface 

 water, 3 from intermediate depths, and 32 from the bottom. In 12 cases, of which 8 

 were surface samples, the alkalinity was over 0*1559 ; and of the 12 cases in which the 

 alkalinity was under 0*1425, no less than 10 were bottom samples. 



It is matter of regret that the density of the specimens of water analysed had not 

 been determined by an exact gravimetric method such as that used by Dr John Gibson 

 in his " Analyses of North Sea Water" {Report of Fishery Board for Scotland for the 

 Year 1889), so that the ratio of chlorine to specific gravity could be used as a basis for 

 estimating the chemical differences between different samples. Hydrometer results, 

 however valuable they may be for sketching in broad differences of salinity, are not 

 sufficiently accurate for this purpose. The number of analyses required to be made in a 

 short time prevented Mr Dickie from even attempting the very elaborate process of 

 determining density by actual weighing. We must therefore confine our discussion to 

 the ratios of the three quantities which were determined. 



In order to see whether there were any marked changes in the chemical composition 

 of the water during the different trips, I have prepared Table XXXVI. , in which 

 account is taken of all the observations for each trip, omitting only those cases of low 

 salinity in which the amount of chlorine was less than 6*0 grammes per kilogramme. 



