389 



of Mollnscan shells. It is almost certain that the rapidity with 

 which dead shells are attacked and dissolved is a simple function 

 of the COg-tension, and the fact, that also in tlie Arctic 

 localities already referred to, the dead shells are scarce and 

 badly preserved, furnishes therefore a strong argument in support 

 of Mr. Jensen's views M 



The last analyses in the table show the influence of abun- 

 dant vegetation and clear sunlight on the tension. Especially 

 in the small and narrow creek on Græsholmen, where the water 

 is probably not so rapidly renewed, the tension reaches a very 

 low value. It is a well-known fact, that the assimilation of 

 higher plants in air is directly proportional to the percentage 

 of carbonic acid, at least at the ordinary low percentages. Sq 



I think it possible that, by a collection of data in this direction, definite 

 relations might be established between the state of preservation of sub- 

 fossil shells and the tension of carbonic acid obtaining during their 

 deposition. 



