378 Pub. Piiget Sound Biol. Sta. Vol. 2^ No. 5 1 



To avoid the errors due to isolated samples the averages of all deter- 

 minations at each of the three stations were compared. It was found that 

 the pH and oxygen content at station Q averaged 7.92-[- and 1.46 cc. per 

 liter; station D, 7.87 (and 4.59 cc. per liter from an average of only 

 three samples) ; and station A, 7.83 and 5.50 cc. per liter. The open 

 water at station Q showed a higher pH than either station D or A, and 

 station D a higher pH than station A. The average oxygen content of the 

 water at stations Q and A was just the reverse. If the averages of all 

 determinations made at the surface, i. e., a depth of 10 centimeters, when 

 the tide is coming in, are compared with the averages when the tide is 

 going out, it is found that the pH and oxygen content at station Q are 

 7.93 — and 4.45 cc. per liter for the incoming tide, and 7.91 — and 4.48 

 for the out-going tide. However, the oxygen for the out-going tide was 

 from an average of only two determinations, one of which was very low, 

 4.18 cc. per liter. Both the oxygen content and pH were higher at a 

 depth of 500 centimeters (see table 3). It is interesting to note that the 

 surface water north of Brown Island at 3:30 P. M, had a pH of 7.96 and 

 an oxygen content of 4.19 cc. per liter. Station D showed an average of 

 7.92 — for the incoming tide and 7.85 — for the outgoing. Station A 

 gave 7.85-)- for the incoming tide and 7.87 — for tlie outgoing. The oxygen 

 content was the reverse, the incoming tide being 4.50 — cc. per liter and 

 the outgoing being 4.48 — cc. per liter. The pH and oxygen content were 

 both almost within the limitsi of experimental error but are averages of a 

 large number of determinations. There seems to be a different relation of 

 the pH to the tide at station D and A. It is worthy of note that the pH 

 lor the incoming and outgoing tides at station A does not go much higher 

 than that of the outgoing tide at station D, and that the pH for the 

 surface water near the village of Friday Harbor, station Y, was found to 

 be at least 0.1 pH lower than the surface water in the open channel near 

 by. Thus, it seems that the condition of the water at station A is influ- 

 enced by that of the water at both stations D and Y, Station B perhaps 

 shows better the effect of an embayment on the condition of the water than 

 either station D or A. The average pH for all determinations at station 

 B was 7.88. The average for the incoming tide was 7.96 and the outgoing 

 7.76. This shows a greater difference than that at station D, and much 

 greater than that at station A. With few exceptions the pH and oxygen 

 content were raised in passing from station A toward Brown Island, and 

 from station D toward the beach. This fact is emphasized by determin- 

 ations made at station F, July 21, 1919, at 10:05 A. ]M., when the tide was 

 coming in. At this time there were two currents meeting at station F. 

 The two currents showed a difference of 0.9 of a degree temperature and 



