232 



and 



DEPTHS OF THE OCEAN 



Pettersson s 



insulating 



water-bottle. 



Pettersson- 



Nansen 



water-bottle. 



along with it the levers, closing both stopcocks simul- 

 taneously. The plate then falls into the position seen in the 

 right-hand figure. This simple arrangement allows of enclosing 

 a water-sample at any depth required. This water-bottle has 

 done very good service ; it was much used on board the 

 " Challenger," and has also — with a few small improvements — 

 been employed a good deal in later times. 



In a stopcock water-bottle of this construction the 

 temperature of the water-sample may alter during the hauling- 

 up process, and it is impossible to get a record of the temperature 

 in situ with the water-sample, without having a special apparatus 

 for the thermometer. Buchanan himself, and later on Nansen, 

 modified this water-bottle by adding an arrangement for a 

 thermometer, which would be reversed the moment the cocks 

 were closed. In the meanwhile Otto Pettersson had adopted 

 F. L. Ekman's old idea of making a water-bottle which should 

 be insulating, so that the water- sample would retain its 

 temperature unchanged, even when drawn up from a great 

 depth. Pettersson availed himself of the circumstance that the 

 water itself is an excellent insulator, its power of conduction 

 being small and its capacity for heat very great. This water- 

 bottle consisted of a bottom-piece, a cylinder, and a lid ; these 

 three parts could be separated by lifting up the cylinder and 

 the lid along two brass rods forming the sides of the encom- 

 passing frame. The cyHnder is a composite one ; inside a 

 strong cylinder of ebonite there are various other cylinders of 

 celluloid and brass, one inside the other like a set of Chinese 

 boxes. Between these concentric tubes are narrow cylindrical 

 spaces which fill with water when the apparatus is lowered into 

 the sea, and in this way a system of excellent water-insulators 

 is formed. The outer cylinder may alter in temperature con- 

 siderably in the course of hauling-up, the inner ones less and less, 

 until in the central chamber the temperature will not change at 

 all for some time, although the water-bottle be strongly heated 

 from without. On the bottom and on the lid Pettersson 

 attached a number of parallel plates, which likewise enclose 

 insulating water-layers. 



Nansen has introduced several improvements, and the latest 

 model — the so-called Pettersson -Nansen water-bottle — is an 

 excellent apparatus, which is now very widely used (see Fig. 

 162). On the left it is seen open, as it is let down into the 

 water ; the lid is suspended in the upper part of the frame, and 

 supports the cylinders as well as a weight hanging below the 



