156 



HYDROGRAPHY. 



It is obvions, however, that a daily period, in so far as the quantity of oxygen is concerned, 

 is manifesting itself at those places where plants are found. This can be accounted for as follows. 

 We collect the values for f—e, from such places where the plankton principally is of a vegetable 

 nature, into two groups, the one containing the analyses made between 12 p. m. (midnight) and 12 a. m. 

 (noon), the second the values for the analyses made between 12 a. m. and 12 p. m. We then get the 

 result that the mean for/— e of the analyses made between midnight and noon will be 0-83, and that 

 of those made between noon and midnight 0-98, and, furthermore, that the ratio between these two 

 values is ri8. In both cases the mean value for/— c is expressed by a positive number, which shows 

 that the entire result of respiration and assimilation with carbonic acid, is a generation of oxygen, 

 which must be supposed to be the consequence of a consumption of carbonic acid. The fact of the 

 analyses made between noon and midnight giving a greater mean ior f—c than those made between 

 midnight and noon, is indicative of the quantity of oxygen having a daily period with 

 maximum between noon and midnight, and minimum between midnight and noon. 

 The phase of the period is supposed to be 6 hours behind that of the illuminative power, so that the 

 cipher indicating the quantity of oxygen passes the mean value at 12 o'clock (noon) and at 12 o'clock 

 (midnight), at which hours the illuminative power has its maximum and its minimum. In the case 

 of the higher plants, the difference of phases between the maximum of the illuminative power and 

 the maximum of the quantity of oxygen is very nearly 6 hours, and a similar ratio applies most likely 

 to the lower plants also. 



If a similar calculation be made for the stations that are lying north of 66° L,at. N., we shall 

 have the a. m. mean-value for/— e to be r2i, the p. m. mean-value 1-37. The ratio between the said 

 values will be 1-13. According to this, it seems as if the period caused by the illuminative power in 

 the generation of oxygen of the plants also is felt here, where, however, it is nearly as light at night 

 as it is in the daytime. The ratio between the mean values for/— e has become less, as it is here 1-13 

 against ri8 in the first-named calculation. That the night has become shorter and lighter, 

 has thus the effect of the aforesaid ratio approaching more to 1, that is to say, the 

 quantity of oxygen that is disengaged during the night, approaches to be equal 

 to the one eliminated during the day-time, in so far as the northern seas are 

 concerned. 



In consequence of the investigations having been made at different places, and in water with 

 plankton that is widely different in so far as quantity and quality is concerned, it is, as a matter of 

 course, quite impossible to draw any conclusion with certainty regarding the question about the course 

 of the daily period, but the results acquired by the formation of the aforesaid mean, furnish us with 

 an answer, which still perhaps may be of some value. 



That the mean for f—e is larger in the northern seas than in the southern ones, shows 

 that the organisms we meet with in the northern seas produce more oxygen than 

 those we meet with in the southern seas, not to be forgotten, in the month of July — how 

 the state of matters is at other times of the year, it is difficult to have any opinion about on the 

 basis of the investigations before us. 



