Hydrographical Observations from the Danmark Expedition. 385 



A characteristic feature at precisely the same depth in both series 

 (56% m.) is the sharp boundary betAveen a nearly fresh, upper layer 

 with a temperature of about — 1° and a lower layer with fairly con- 

 siderable amount of salinity, which from 70 m. downwards as far 

 as the observations were carried Avas nearly uniform, whilst the tem- 

 perature increased. This warm and salt bottom-water had a very 

 strong smell of hydrogen sulphide. 



The diagrams show, that the salt and fresh layers were sharply 

 bounded towards each other and thus only became mixed to a small 

 degree. 



The fresh layer was probably renewed by downflow from 

 the glacier at the head of the lake, and the outflow to the sea 

 through the river meant a certain amount of circulation. As 

 the salt bottom-water smelt of hydrogen sulphide, it was probably 

 stationary. 



The question is now, where this considerable layer of salt and 

 w-arm water came from. The salinity (ca. 28 p. m.) was slightly lower 

 than the average salinity of the sea outside. There could not be any 

 constant communication between the two, however, since the lake, 

 as already noted, lay ca. 4 m. above the level of the sea. Further, 

 the temperature of the warm bottom-layer was considerably higher 

 than the average temperature in the sea even at the hottest time in 

 summer. 



There was a possibility, that the salt water came from salt in 

 the ground and not at all from the sea. To get this question decided, 

 the samples of bottom-water from the two stations in the lake were 

 subjected to a more exact chemical analysis bj?^ Dr. Niels Bjerrum 

 in Copenhagen. 



The result of his analysis was the foUowing. 



Investigation of two samples of water from Greenland lakes. 



The investigation, which was to determine, whether the very 

 saline samples of water had the same composition as sea-water, gave 

 the result, that this was the case. This was decided by the determina- 

 tion of the chlorine, traces of sulphuric acid, sodium, magnesium, 

 calcium, potassium and of the density. 



The samples, which had been kept in soda-water bottles (% 

 litre) with porcelain stopper tightened by a rubber ring, were filtered. 

 Then the amount of sulphates in 50 cc. was determined by precipi- 

 tation with barium chloride and weighing as barium sulphate. The 

 chlorine was determined in 5 cc, which were weighed and titrated 

 with 0.1 normal silver nitrate solution with potassium Chromate as 

 indicator. The calcium was precipitated from 50 cc. by ammonia 

 and ammonium oxalate and weighed as oxygen. The same process 

 XLI. 25 



