1920 Poicers; on Condition of Sea-zcater SI 5 



workers (Xatterer 1892, 1893; Palitzsch 1911a, 1912; Henderson and 

 Colin 1916; Gaarder 1917). These have found a decrease in the pH 

 Oi- an increase in the hydrogen-ion concentration with depth. On July 19, 

 1918, when the tide was coming in. stations G and I showed a more or 

 less uniform decrease of the pH with depth and a still more uniform 

 decrease in the oxygen content. On the other hand, at station H the 

 relations both in pH and oxygen content were reversed, though the dif- 

 ferences were far less than those found at stations G and I. On July 

 20, 1918, station H showed a uniform decrease in the pH with depth but 

 the oxygen content was reversed, while station J showed at first a decrease 

 ill the pH with depth which was followed by a rise at greater depths. 

 The oxygen content showed no uniformity whatever. Again on July 22, 

 1918, at station H. there was a decrease in both the pH and the oxygen 

 content down to 80 meters and then a rise in both down to 160 meters. 

 By the afternoon of the same day there seemed to have been a general 

 mixing of the water at all depths as shown by the pH and oxygen content. 

 At station G, on July 11, 1919, there was a rise in the pH down to 40 

 meters with the oxygen content within experimental error, the lower being 

 toward the surface. Downward this was followed by a decrease in the 

 pH down to 100 meters, then a rise down to 1 10 meters. The oxygen con- 

 tent showed still less uniformity. The only conclusion to be derived 

 from these observations is that the water at different levels has different 

 sources. That is, the water from different portions of the Sound, for 

 example from different embayments, at times may become more or less 

 stratified, due to the physiograjDhy of the region. The specific source of a 

 given layer of the water depends upon a number of factors, chief of which 

 are the wind, its velocity and direction, and the stage of the tide. Again 

 the condition of the water from these various sources depends upon their 

 localit}', the weather, the tide in its relation to day and night, and the 

 season of the year (Moore, Prideaux and Herdmaii 1915). The condition 

 of the water depending upon the tide in its relation to day and night will 

 be better understood after we have discussed the effect of vegetation upon 

 the liydrogen-ioii (■(uicciilration and oxygen content of the water. Finally, 

 at certain stages of the tide the water of the channels of the Sound may be 

 more or less completely mixed at all depths. This conclusion is borne out 

 botli by the observations made on tlie pH and oxygen content of the water, 

 and bj the fact that at times tiiere are wellings up of the water thruout 

 ihc main channels of tlie Sound. From the observations made, no curve 

 could be formulated to show tlie relation of the pH and oxygen content 

 at .different dc))tlis, aiKi otiit r factors. Tlie coiitrolliMg factors are verv 

 complex. 



