I5 HYDROGRAPHY. 



values would only be subject to so small a difference that it would be of no consequence at all, and 

 it is for the same reason that no regard has been taken to the moisture of the air at the calcula- 

 tion of b. 



The objection may perhaps be made that it is not appropriate to have recourse to foreign 

 observations — such as Bamberg's — at the indication of the quantity of nitrogen which the water con- 

 tains when it is saturated, for it is a matter of course that there is a possibility of systematical errors 

 occurring, when comparing ciphers due to different observers that have used different instruments. 

 But to this I shall confine myself to say that even if the numerical values be made a little larger or 

 smaller, such a thing will not have any influence on the conclusions set forth in the foregoing. 



It will be seen from what has been said in this chapter, that the rapidity with which 

 the heating of the surface-water has taken place, can be ascertained, if we know the 

 supersaturatiou the said water has been subject to, and in case of our having many 

 observations, we have likewise a means to explain from what quarters the water at 

 the different places has its origin, provided that the whole does not form a regular 

 uniform system. 



THE AMOUNT OF NITROGEN AT THE BOTTOM. 



In the chart, plate XXXV, the amount of nitrogen is noted immediately on the right hand 

 side of the places where the stations are noted, uppermost to the right the temperature of the water, 

 and nethermost on the same side the temperature of absorption. Across each of the places marking 

 the stations, an arrow is drawn, which is pointing in the direction the current is supposed to have 

 run on the basis of these observations concerning supersaturation and incomplete saturation. The 

 extent of these qualities is approximately indicated by the length of the arrow. The stippled arrows 

 show in the same manner the direction of the current at a depth of 400 or 600 fathoms (753 or 

 1 130 metres); which direction, in all the cases that have been subject to investigation, is seen to coin- 

 cide with the direction of the current at the bottom. 



As already mentioned in the chapter on the determination of the amount of nitrogen in the 

 surface-water, we cannot take it for absolutely granted that water in the depths, which has come from 

 surface-layers in cold regions of the sea, should be supersaturated with nitrogen. If such water, on 

 the contrary, proves to be supersaturated, it must probably be due to its having been subject to heating 

 while it was making its way from the surface to the depth. It is not likely to be supposed that water 

 should leave the surface while it is subject to heating, and in consequence of this supersaturated. 



By the putrefaction of organisms, the amount of nitrogen may be increased, and a supersatura- 

 tion be brought about It is to be supposed that this has been the case at the stations 67 and 80, 

 which show such an extraordinarily large amount of nitrogen. The water samples contained mud from 

 the bottom, and must therefore belong to the very lowermost strata, where the greater part of orga- 

 nisms is to be found. Other muddy samples, such as at the stations 45, 48, 75, 78 and 89 did not 

 deviate from the usual type of samples, but it is a matter of course that these samples could not be 



