74 



Papers from the Marine Biological Laboratory at Tortugas. 



SALINITY. 



The data in table i show that there is no significant or regular difference 

 in chemical composition of the incoming and the outgoing tide. The 

 average chlorine content of the flood water is 19.936 grams per kilogram 

 and the maximum range is only 0.12 gram per kilogram, while the content 

 of the slack water is 19.932 grams per kilogram with a maximum range of 

 0.13 gram per kilogram. The close agreement of these averages, the narrow 

 range of the values, and the insignificant differences between daily tide 

 contents indicate that there was no essential difference in concentration 

 of the waters during the period in which the samples were collected. These 

 results, with those in table 2, show, however, that the salinity of the sea- 

 water at Tortugas is slightly greater than that of average ocean-water. This 

 greater concentration is doubtless due to high rate of evaporation in the 

 comparatively shallow water. 



Table 2. — Chlorine Content and Salinity of Sea-Water at Tortugas, Florida. 

 [Grams per kilogram.] 



Source. 



Date. 



Ofif Loggerhead Key' .... 

 Reef, Loggerhead Key2 . 

 Southwest Channel' 



Do.= 

 Wharf, Fort Jefferson^... 



Ofif Garden Key' 



Do.' 



Moat, Fort Jefferson^.... 



Do.' 



Do.' 



Do.' 



Do.' 



Do.' 



Do.' 



Do.' 



Content of ocean water'* . 



1910 



June 1912 



Average for May and June 1913. 



June 1912 



Do 



May 25, 1913 



June 14, 1913 ■ 



June 1912 



During rain, Jan. 27, 1913 



After rain, Jan. 27, 1913 



During rain, Feb. 27, 1913 



After rain, Feb. 27, 1913 



May 25, 1913 



June i4i 1913 



June 15. 1913 



Chlorine. 



19.60 

 19-95 

 19.93 

 19.99 

 19.99 

 19.84 

 19.96 

 20.09 

 19.61 

 19.60 

 19.83 

 17.79 

 19.67 

 19.83 

 19.19 



19.386 



Salinity. 



35.41 

 36.04 

 36.01 

 36.11 

 36.11 

 35.84 

 36.06 

 36.29 

 35-43 

 35.41 

 35.82 

 32.14 

 35.S3 

 35-82 

 34-67 



35.02 



' Computed from report of analysis by G. Steiger, of the U. S. Geological Survey Laboratory; pub- 

 lished in The Data of Geochemistry, by F. W. Clarke, Bull. U. S. Geological Survey, 491, p. 113, 1911. 

 2 Tested at the Plymouth (England) laboratory. 

 ' Tested by R. B. Dole. 

 ■* Standard P7 2/2, 1912. 



ALKALINITY. 



The average alkalinity of water from the Southwest Channel, 0.0400 

 OH gram per kilogram, is that given by Allen and others for normal sea- 

 water.^ The average alkalinity of the flood water, 0.0401, and that of the 

 slack water, 0.0399, differ from each other much less than the average 

 deviation of individual observations (±0.0008), and agree with the esti- 

 mates of alkalinity of the composite flood- and slack-tide samples recorded 

 in the last two lines of table i . The alkalinity of these waters seems to be 

 practically the same as that of normal sea-water. 



The average total content of carbon dioxide of the incoming water is 

 essentially that of the outgoing water, and though the recorded values differ 

 somewhat from day to day the range is not very great or very significant; 

 there is no regular excess of the values of one set over the other. Though 

 the probable error of individual determinations, about 0.0020 gram per 



1 Allen, E. J., and E. W. Nelson. On the artificial culture of marine plankton organisms. Quart. 

 Journ. Micros. Science, vol. 55. pt. 2, June 1910. 



