j , , HYDROGRAPHY. 



SECTION XXV. 



From Iceland in a curve round the southern point of Greenland. 



This section deviates from the other sections by reason of its horizontal extent being drawn 

 on a scale which is '/, of the scale of the chart on plate III, while that of the other sections is 3/ 2 of 

 that scale, and furthermore thereby that it is not approximatively lying in a plane — which is the 

 case with the other sections — but in a curved surface south of Cape Farewell. 



The eastern part of the section is also to be found in section VI, and it has already been 

 described there. In section XXV we meet with the curved 35 - 25 isohalines again, which show how 

 the water is ranging itself in layers at the boundary between the basin of the Atlantic and that of 

 the Denmark Strait. The 35*00 isohaline is stretching from the surface to the bottom in the shape 

 of an S, and west of this isohaline, the salinity is nearly everywhere lower than 3 5'00. 



It will be seen from the bottom-curve that the section goes across a submarine ridge, situated 

 between the stations 20 and 21, and probably a continuation of Cape Farewell, in a southerly direc- 

 tion. It will be noticed that the temperature at the bottom is lower west than east of the ridge, and 

 the same applies to all the salinities. There are, however, a few exceptions to this rule. Station 20 

 for inst on the eastern side of the ridge, has a low temperature, while station 22 on the western side 

 of the ridge has a high salinity. Here we meet with a phenomenon, which is exactly the same as 

 the one that applies to the state of matters round all the submarine ridges which have been subject 

 to investigation by the expedition, and this is, that even if such a ridge is forming a bound- 

 ary between water of different qualities, it will never for all that form an insur- 

 mountable barrier; water will always pass across the ridge in both directions. 



When speaking about the sections X, XI and XII, we called the water in the middle part of 

 the Denmark Strait that had a smaller salinity than 35'25 basin-water. We must therefore, judging 

 by the salinity in section XXV, come to the conclusion that this section, from station 18 to 

 station 21, is lying in the basin-water. The basin of the Denmark Strait has, as we know, a 

 natural boundary to the westward in Greenland and the ridge that probably is proceeding from Cape 

 Farewell in a southerly direction. We shall find that the observations represented in section XXV, 

 agree very well with the theory I have put forth on page 114 concerning the currents in the Den- 

 mark Strait. 



Is has been pointed out how the basin-water arose : The western branch of the Irminger Current 

 is by the East Greenland Polar Current turned to the southward, and during its course along this latter 

 it is getting cooled, while at the same time its salinity is decreased, so that the part of it, which by 

 the Atlantic-water is forced to run east, afterwards north, and made to take part in the rotation in 

 the Denmark Strait, exactly has the same qualities as the basin-water. 



As the water, while it is moving in an easterly and northerly direction at the side of the 

 Irminger Current constantly is under the influence of the Atlantic-water, we must be led to believe 

 that its temperature and salinity is growing from west to east. Looking at section XXV, it will be 

 seen that this conclusion is exactly in conformity with the actual state of matters, in so far as the 

 said tract of the sea is concerned. 



