Hydrographical Observations from the Danmark Expedition. 



303 



The tent ought to be able to close quite tightly, as it is other- 

 wise impossible to maintain a positive temperature inside on specially 

 cold days. Drum and wire should naturally be as light as possible, 

 and similarly the lightest model of water-bottle (Ekman's) should be 

 used. All rods or screws of metal, which have to be handled, should 

 be covered with wood. 



As bottles for the samples small medicine bottles of 30 gm. will 

 be sufficient. Our half-litre bottles weighed far too much. It should 

 be possible to pack the bottles in a small, light box, which can be 

 closed, so as to be impenetrable in snow-storms, and each bottle 

 should be so well j^acked, that it will not break even if the sledge 



Fig. (i. Hydrographical worlc on the ice from a sledge; C. B. Thostrup phot. 



is overturned. It should be remembered, not to fill the bottles quite 

 full with water, as this expands on freezing and would thus break 

 the bottle. Before departure the bottles should be marked with string 

 clearly and distinctly round the neck or in some other way. Spring 

 is the best time for making hydrographical investigations, as the direct 

 sunshine on the dark water-bottle is sufficient to keep it thawed, even 

 when the sling-thermometer shows an air temperature of — 10° to 

 -15°. 



3. Investigation of the water-samples. 

 Titration. 

 The water-samples collected on the outward voyage and those 

 taken later in 1906 and 1907 were titrated onboard by myself. 



