3l8 VICTOR E. SHELFORD AND EDWIN B. POWERS. 



dioxide being wanting. The half bound carbon dioxide was 

 24.2 c.c. per liter and the fixed 28.6 c.c. The oxygen was less 

 than 0.5 c.c. per liter (for methods see Birge and Juday, '11, 

 pp. 13-21). Such water is unsuitable for biological purposes and 

 was used in these experiments only after aeration by running it 

 slowly over an inclined board ten inches wide and four feet long. 

 After this aeration the oxygen content was, at 13° C, 4.9 c.c. 

 per liter and the excess of other gas was removed, but the water 

 still remained alkaline. 



The sea water supplied at the station building was pumped 

 from a depth of about four feet below mean tide. It was retained 

 in a wooden tank, being pumped twice per day, in the evening 

 and in the morning. Upon standing in the tank the temperature 

 rose from 11° to nearly 15° on warm days. 



The oxygen was determined by the Winkler method. In no 

 case was the sea water from the tank or from the bay from which 

 it was pumped, saturated with oxygen even in samples collected 

 at the surface. The only surface collection made that showed 

 saturation according to the tables of Fox (see Murray and Hjort, 

 '12, p. 254) was from the strong tide rips off Point Caution at 

 5:30 P.M. Collections from the bottom of sandy shores among 

 Ulva were super-saturated. 



Chlorine was determined by titrating with silver nitrate. It 

 usually amounted to about 16.93 grams per liter. It was usually 

 a little higher in water from the tank than in water collected 

 from the sea. The determination of carbon dioxide was made 

 by the method in common use in fresh water. The sea water 

 was titrated with 2V normal solution of sodium carbonate, with 

 phenolphthalein as an indicator. The water was usually 'acid in 

 reaction indicating about 1.7 c.c. per liter of free carbon dioxide. 

 The half bound and bound carbon dioxide as indicated by the 

 method used by Birge usually amounted to 25.3 c.c. per liter 

 each. There was considerable uniformity in the results of such 

 titrations and while the method is not especially accurate the 

 lack of oxygen common in the water would indicate an excess 

 of free carbon dioxide over that commonly reported for sea 

 water. The correctness of these figures is further suggested 

 by the slight alkalinity of the water taken from the vicinity of 

 green algae and containing an excess of oxygen. 



