CH. l] THE EXPLORATIOX OF THE SEA 7 



being suspended these rings are secured to the lead by means of 

 a sling which passes over each of the notches in the plunger. It 

 will easily be seen that when the lead touches the bottom the 

 tension of the line decreases and the plunger drops within the 

 tube. When the notch in which the sling is placed falls below the 

 opening of the tube it releases the weights, which then drop off 

 and are lost. But in falling off they push down the lever of the 

 stop-cock which then closes. The tube has however been pushed 

 down into the sea floor and is filled with a sample of the deposit 

 there, and the closing of the cock prevents this from falling out 

 when the line is hauled up again. 



The water sample bottle and the thermometer. A simple 

 sounding thus gives us a knowledge of the depth of the sea and also 

 a sample of the deposits lying on the sea floor. A " hydrographic 

 sounding " gives us a sample of the sea water at the bottom or at 

 any required depth, and in addition the temperature of the water 

 in situ. The water sample is to be used for the determination of 

 the density, salinity, gas contents, or any other property or 

 constituent of the water. There are a host of water bottles 

 (Buchanan, Ekman, Jacobsen, Kidder-Flint, Meyer, Mill, Regnard, 

 Sigsbee, Wille, and probably others). It will serve the reader 

 best if I describe only the water bottle which is used by the 

 vessels of the International Fisheries Investigations, and which was 

 devised by Nansen and Pettersson. 



This instrument is represented diagrammatically in Fig. 4. It 

 consists essentially of two brass rods connected together at either 

 end, and between which slides an open cylinder, which is the actual 

 bottle. Fixed between the lower ends of these rods is a stopper 

 which can accurately close the lower end of the cylinder; and 

 sliding freely on the rods above the cylinder is another similar 

 stopper which can close the upper end of the bottle. The wall of 

 the latter consists of four concentric cylinders of metal and 

 ebonite alternately : each stopper consists of a metal cap carrying 

 three rubber discs and it is the latter which fit into the open ends 

 of the bottle. The upper stopper is perforated to receive a 

 thermometer, and the lower one is provided with a stop-cock. 

 When the bottle is about to be lowered into the sea the parts are 



