320 THE VOYAGE OF THE " FRA]M " 



the cylinder at the required depth remains in it while it 

 is being heaved up, and is collected in bottles. When 

 tlie apparatus is released, the column of mercury in the 

 thermometer is broken, and the temperature of the water 

 is read at the same depth as the water is taken from. 



The release takes place in the following manner: 

 when all the cylinders have been lowered to the required 

 depths, they are left hanging for a few minutes, so that 

 the thermometers may be set at the right temperature 

 before the column of mercury is broken. Then a slipping 

 sinker is sent down the line. When this sinker strikes 

 the first apparatus, a spring is pressed, a hook (e) which 

 has held the cylinder slips loose, and the cylinder turns 

 completely over (Apparatus I.). As it does this, the 

 valves, as already mentioned, close the ends of the 

 cyhnder, which is fixed in its new position by a hook in 

 the bottom of the frame. At the same instant the 

 slipping sinker that hangs under Apparatus I. is released, 

 and continues the journey to Apparatus II., where 

 the same thing happens. It is then repeated with 

 Apparatus III. When they are all ready, they are 

 heaved in. 



By holding one's finger on the line one can feel, at all 

 events in fairlv calm weather, when the sinkers strike 

 against the cylinders; but I used to look at my watch, 

 as it takes about half a minute for the sinker to go down 

 100 metres. 



The necessary data are entered in a book. 



