HYDROGRAFI. 2 c 



THE INVESTIGATIONS, AND HOW THEY WERE 



PERFORMED. 



When I had the honour of being appointed to undertake the physical investigations on board 

 the cruiser Ingolf during its voyages in 1895 and 1896, I was totally unacquainted with 

 hydrographical work, and the knowledge I had occasion to acquire of hydrographical literature before 

 our departure in 1895, was but a trifle. It is therefore to Cpt. Wandel that we are indebted for what 

 has been done, who decided the character of the. observations that were to be made, and who always 

 was ready to assist me by word and deed during my work in the service of the expedition. 



OBSERVATIONS OF TEMPERATURE. 



During the first voyage in 1895, my work on board was confined to observations of tem- 

 perature, determinations of the specific gravity and the amount of chlorine of sea- 

 water, and to take samples of water in bottles and exhausted glass-balloons. During the voyage of 

 the second year, the gases held in the sea-water were analysed immediately, in consequence of which 

 it was not considered necessary to take samples of the last-mentioned description. For the deter- 

 mination of temperatures in the depth, we used the turning thermometers mentioned on page 

 8, but on account of the zero-point-variation proving to be rather considerable, and specially on the 

 thermometers employed on the first voyage, the zero-point was determined whenever there was an 

 occasion to do so. For this object, clean snow fetched from the mountains was used. To convince 

 myself of the snow being sufficiently clean, I made it subject to a trial with a solution of silver 

 nitrate. This trial proved to be sufficient, as no difference could be observed between the melting 

 point of snow that did not give a distinct sediment when a solution of silver nitrate was applied to 

 it, and ice formed of distilled water. As a rule 110 more than a fortnight elapsed between 

 two zero-point corrections. In spite of the thermometers used on the second voyage being 

 made of normal glass, and in consequence of this not giving so large zero-point variations, a correc- 

 tion became necessary for all that now and then, as the alterations were much larger than in a com- 

 mon thermometer made of the same kind of glass. Before the departure these thermometers were 

 tried for pressure. In want of another apparatus, I had a cast iron tube with a solid piston made for 



The Ingolf-Expedition. I. 2. 4 



