PHYSICAL OCEANOGRAPHY 



233 



apparatus. When a messenger is sent down the line and strikes 

 the water-bottle, the Hd is released, and the weight draws both 

 lid and cylinders down, clasping the 

 apparatus together and closing it her- 

 metically. The right - hand figure 

 shows the water-bottle closed and 

 ready for hauling up. The Nansen 

 thermometer is seen in the left- 

 hand figure, and is — as mentioned 

 above — a thin delicate instrument, 

 fitted inside a strong protective glass- 

 tube in order to withstand the enor- 

 mous pressure of the deep sea. The 

 Pettersson-Nansen water-bottle is so 

 well insulated that the temperature of 

 the water-sample is not influenced 

 from without, even when being hauled 

 up from a depth of 1000 metres. 

 But the temperature is lowered 

 slightly, in consequence of the reduc- 

 tion of pressure during the process of 

 hauling up, as has already been men- 

 tioned. This circumstance asserts 

 itself quite appreciably in the case of 

 the insulating water-bottle when used 

 at great depths. The water-bottle 

 is, however, fitted with a frame for 

 carrying a reversing thermometer, so 

 that a double determination may be 

 made. During the "Michael Sars " 

 Expedition we very often employed 

 the insulating water-bottle, and took 

 temperatures both with the Nansen 

 thermometer and with the Richter 

 reversing thermometer simultaneously. 

 As an example, an observation made 

 at Station 10 1 in 1400 metres may 

 be mentioned : after correction the 

 Nansen thermometer read 4.45'' C, 



the Richter thermometer 4.59° C, that is 0.14' C. lower in the 

 first case than the second. The water in the water-bottle 

 should, according to the calculation by Lord Kelvin's formula, 

 have been cooled 0.12° C. ; granting that the determinations 



Fig. 162. — Pettersson - Nansen 



Water-Bottle. 



Shown open in the left-hand figure, and 



closed in the right-hand figure. 



