of the Surface Water of the Atlantic and Pacific. 65 



reading would be 8.21; and for salinity 30, if the tubes read 8.22 the 

 true Ph would be 8.24. These corrections are, however, of minor 

 significance for Pacific sea-water, for one can not read the Ph on the 

 colorimetric tubes to within 0.02 Ph, although one can detect a 

 difference of 0.03 Ph. 



Upon being taken from the sea, the water was at once tested for 

 temperature and Ph, and a sample was preserved in a rubber-stop- 

 pered bottle for determination of salinity; this was done as soon as 

 possible after the end of the voyage. Some of the samples were 

 tested by Professor L. R. Gary for oxygen, using Winkler's method, and 

 in all such cases the water was tested immediately upon being taken 

 from the ocean. 



OBSERVATIONS. 



In connection with these tests of hydrogen-ion concentration, the 

 electrical conductivity of the sea-water off Tutuila, Samoa, and at 

 Tortugas, Florida, was determined by Kohlrausch's method, using 

 a Wheatstone bridge designed by Leeds and Northrup for this special 

 purpose, and having a tunable telephone for a detector. As will 

 be seen in table 1, the sea-water of Tortugas Table i 



has a higher coefficient of electrical conductivity 

 than that of Samoa, due to the higher salinity of 

 Atlantic water. The table gives the data of 

 electrical conductivity of Samoan sea-water at 

 various temperatures, that of N/10 KCl being 

 unity at the corresponding temperature. This 

 sea-water was collected one-fourth mile east of 

 Cape Matutula, the easternmost point of Tutuila, 

 on April 28, 1917. The salinity was 34.83, cor- 

 responding to a chlorine content of 19.28 grams 

 of chlorine in 1,000 grams of water. The hydro- 

 gen-ion concentration was 0.563 X 10-^ (Ph 8.25) at 28.2° C. The 

 second column shows the electrical conductivity of sea-water, that of 

 N/10 potassium chloride at corresponding temperature being unity. 



At Tortugas, Florida, the conductivity of sea-water having 20.06 

 grams of chlorine in 1,000 grams of water, corresponding to a salinity 

 of 36.24, was determined by the same apparatus, and with a portion 

 of the same KCl solution used in Samoa. It was found that the 

 conductivity of this Tortugas sea-water at 25° C. was 4.163, and at 

 30° C. it was 4.117 times as great as that of N/10 KCl solution at 

 the same temperature. 



The average of 62 observations gives 34.87 as the salinity of the 

 surface-water between the Hawaiian Islands and Samoa, whereas 

 in the American tropical Atlantic the salinity is above 36. 



As McClendon states, temperature is the most important factor 

 determining the Ph of the surface water of the sea; for, as the temper- 



