CH. l] 



THE EXPLORATION OF THE SEA 



9 



fixed in the position shewn by means of a spring catch not shewn 

 in the diagram. The whole is attached to a steel wire rope and 

 when it has been lowered to the desired depth a " messenger " is 

 allowed to slide down the line until it strikes against the catch, 

 when the cylinder slides down the rods until it is closed by the 



Fig. 4. The Nansen-Pettersson water bottle. Some parts are omitted. ^ , ^ are the 

 stoppers ; B the concentric walls of the bottle ; C the outer case of the latter ; 

 D, D, D, D the ends of the stoppers and the bottle, these parts slide on the 

 brass rods i? ; T is the stop-cock through which the water sample is withdrawn ; 

 Th is the thermometer, and W the weight which carried down the apparatus. 



