144 



HYDROGRAPHY. 



matively a line of demarcation between the two species of water in these seas. The last named of 

 these observations were made by Danish vessels, and entered into meteorological journals made exclu- 

 sively for the use of the Meteorological Institute. The institiite has in its annual publication, Meteoro- 

 logisk Aarbog 1892* Tredie Del pag. XII and «Meteorologisk Aarbog 1895* Tredie Del pag. 5, given 

 an account of these determinations. The mean values of the observations of temperature can be found 

 in the tables of these yearly publications. The manager of the Meteorological Institute Mr. Adam 

 Paulsen has been kind enough to place the said journals at my disposal, and I have selected those 

 observations that are lying within 6i° — 68° Lat N. and 5 — 15 L. W. of G., as it appears that the 

 aforesaid boundary line between the two species of water, always is met with inside this region of the 

 sea, provided of course that it be possible to fix such a line of demarcation. 



Of about 650 observations for 1896, those that are pertaining to one and the same month, have 

 been laid down in the same chart, and a line has been drawn through those points, at which a quick 

 transition from the surface temperature of the Atlantic to lower temperatures has manifested itself. 

 This line is then regarded as the line of demarcation between Atlantic-water and ice-water. Taking 

 the different circumstances into consideration, it is a matter of course that the observations during 

 the winter months only have been very few, and as the observations have not, upon the whole, been 

 carried out on a regular plan, in so far as we may desire to avail ourselves of them for the aforesaid 

 purpose, it can often be attended with difficulty, and it is sometimes even entirely impossible to fix the 

 boundary line between the two species of water with tolerable exactues. 



In the chart on plate XXXIII where the boundary line is drawn for each of the months April, 

 May, June, July, August, and October, only so great a part of the line has been laid down that the 

 parts which have been drawn with complete exactness show the direction of the motion of the bound- 

 ary' line together with the approximate extent of the deviation the line has been subject to. It can be 

 seen by this chart that the boundary line in the course of a short time can alter its form conside- 

 rably, specially from April to June and from June to July. In consequence of this, we cannot fix a 

 line of demarcation that applies to a whole month, but we must have the determinations by which 

 this line is represented, made at more frequent intervals of time than a month or months, if we want 

 to give a true and faithful illustration of the continued change the boundary line must be subject to. 



In the chart I have therefore as far as possible drawn the extreme positions of the boundary, 

 so that the line of demarcation drawn for April, in reality is the northernmost position of this line in 

 April. The boundary line for June has been drawn on the basis of the situation from the 2& to the 

 5th of June, while this line, if we had availed ourselves of observations from the 20th of June, ought 

 to have been laid as far northerly as for the month af July. Hence the figure will give us a 

 representation of the amplitude of the deviations the boundary line has been sub- 

 ject to. I take it for granted that it must afford the greatest interest to know the extreme positions, 

 and specially the southernmost ones. 



The deviations the boundary line has been subject to, cannot be called great, 

 and in a south-westerly — north-easterly direction they will take place within a range 

 of scarcely 100 miles, but sometimes they occur in a very short time, and the question will 

 then arise whether we shall be able to find a variation that is characteristic for a certain time of the 



