!6o HYDROFRAPHY. 



alterations may take place frequently and in a short time. A change of this kind may 

 for inst be caused by the plankton, or only part of it leaving the surface, even if it only be for a 

 short time, and in case of onr leaving out of consideration the changes that might take place at the 

 surface on account of the motion of the plankton in the water, a real change in the nature of the 

 plankton is not improbable, as the plankton that is present in an abundant quantity dies, and is re- 

 placed bv other plankton, which then in its turn becomes predominant in respect of quantity 

 and quality. 



THE REST OF THE ANALYSES. 



Notwithstanding the fact that we cannot attach any importance at all to the absolute indica- 

 tions at the determinations of the carbonic acid in consequence of the method employed at the analyses, 

 we ma) r for all that suppose the relative determinations to be tolerably reliable, as all of the analyses 

 are made in the same manner, and errors at repeated analyses never amount to 2 / I0 of a cubic 

 centimetre. 



If we divide all the values for the amount of carbonic acid in the surface-water into two 

 groups, according to the sign lorf—e, by which in the one group we get the amount of carbonic acid in 

 water with oxygen in excess, and in the other the amount of carbonic acid in water with an oxygen- 

 deficit, and we take the mean of the values in each of these two groups, we shall have for f—c posi- 

 tive, C0 2 = 39/8, for/— e negative C0 2 = 417. We see by this that there is observed a smaller 

 quantity of carbonic acid at those places where we have found oxygen in excess, than at the places 

 where an oxygen-deficit is manifesting itself. We know, according to what has been explained in the 

 foregoing, that the plankton has an influence on the quantity of carbonic acid, and we see, moreover, 

 that even if other causes exercise their influence on the result, they are not for all 

 that sufficiently active to conceal the influence of the plankton. 



We may perhaps even be quite justified in making the assumption that the organisms in the 

 sea are those factors that have the greatest influence in so far as regards the quantity of carbonic 

 acid existing. On the basis of this conclusion the irregular distribution of the carbonic acid 

 can easily be understood, as the quantity of carbonic acid at a certain place, is not 

 only dependent on the plankton that is present at the moment of observation, but 

 also on that which has been present before in the same water. Taking into consideration 

 at the same time, how quickly the quantity and nature of the plankton is changing, and that at two 

 places lying close to one another, and which we should think would have the same conditions for 

 organic life, the plankton can be of quite a different nature, then the variations in the quantity of 

 carbonic acid, apparently in opposition to the laws of nature, can easily be accounted for. 



There is, therefore, at the single observations of plankton very little possibi- 

 lity of finding a slight quantity of carbonic acid where we meet with vegetable plank- 

 ton, and a great quantity of carbonic acid where the plankton is of an animal 

 nature. It is only, as has been stated above, by taking the mean of many observations that such 

 a state of matters is manifesting itself. 



