13â FRIDTJOF NANSEN. 



ihe surface^ for (1) the splits in the india-ruhber plates of the 

 hd, necessary for the insertion of the thermometer formed an 

 open communication between the upper, and possibly cooled, 

 waler-strata and the central tube; (2) the insertion of the ther- 

 mometer would more or less stir the water-strata in the bottle; 

 and (3) the inserted thermometer may change to some extent the 

 temperature of the water in the water-bottle, or will at any rate 

 require a long time (several minutes) to assume the temperature, 

 and in the mean time the water enclosed in the water-bottle 

 will more or less change its temperature by emission and 

 transport of heat. It therefore seemed to me to be an essential 

 point, that instead of waiting for the thermometer to assume its 

 temperature on deck, it would be better to send it down with 

 the water-bottle to the desired depth, there let it assume its tem- 

 perature, and read it off as soon as the water-bottle arrived at 

 the surface. I had therefore several thermometers made for 

 this purpose by C. Richter in Berlin. The thermometers were 

 protected by an outer tube of strong glass, about 13 mm. in 

 diameter, which would be able to withstand the pressure of the 

 water at the bottom of the sea. These glass-tubes were evacuated, 

 in order to reduce their conduction of heat and were filled with 

 mercury at one end, round the bulb of the thermometer, in order 

 to make the latter more sensitive. As the thermometer could 

 not without inconvenience be made more than a certain lenght, 

 and as I wished the degree Centigrad of the thermometer scale 

 to be one centimetre in length, in accordance with the program 

 of the International Conference for Oceanic Research at Stock- 

 holm in 1899, I had two sets of thermometers made, one for 

 temperatures ranging between — 3°C and -\- 8°C, and another 

 for temperatures ranging between + 6°G. and -|- 17°G. These 

 thermometers were fixed by a special arrangement, ensuring 

 water-tightness, in the lid of the water-bottle (see PI. 2, Fig. 1). 

 They worked very well and gave accurate resnlts. 

 ' Cfr. Nansen ]. c, pp. 6 et seq. 



