374 



will generally be somewhat higher. I have found a tension of 

 in the bottom of a little creek on the river Kuganguak, 

 луЬеге the water was perfectly at rest. In the bottom of rapid- 

 flowing glacier-rivers i have found varying tensions up to 3. 

 The percentage of oxygen in the air-bubbles is generally a 

 little below that of the atmosphere — 20.75 %. 



Peculiarly instructive are some analyses of air-bubbles from 

 a very small pond, about 1 foot deep, which had, probably for 

 a couple of months, been shut off from the Kuganguak. In 

 this pond the bottom was covered by a thick and rather solid 

 organic pellicle protecting the water of the pond from contact 

 with the basaltic soil. The pellicle was covered Avith innumerable, 

 small air-bubbles, a sample of which was collected and analysed. 

 When the pellicle was removed bubbles of air could be col- 

 lected from the bottom itself, and by means of a stick I suc- 

 ceeded in collecting air-samples from a depth of about 1 foot. 

 The analyses showed : 



Air from the organic pellicle 



Two samples of air from the bottom . 

 Air from the depth of one foot 



CO., o/ooo O, o/o 



f 2 



7 



24.60 

 30.83 

 20.07 



2.14 



Tp. 



11.1' 



! 11.1' 



Though assimilation, as seen from the percentage of oxygen, 

 was distinctly preponderant over respiration in the water of the 

 pond the tension of carbonic acid was hardly below that of the 

 atmosphere, while in the basaltic bottom it was much lower. 

 In the deeper stratum organic life, probably bacteria, must, I 

 suppose, have been the cause of the comparatively high tension 

 of carbonic acid as well as the extremely Ioav percentage of 

 oxygen. 



The influence of vegetation on the tension of carbonic 

 acid is shown by some analyses. Bogs are of very common 



