178 BULLETIN OF THE 



Working. 



The cup comes to the surface filled with water, the screw-cap down on 

 the upper valve, and the propeller resting on the cap. To get the water 

 out, first sci'cw up the propeller until it takes on the thread of the shaft ; 

 then screw up the screw-cap until it uncouples from its thread. The 

 valves may then be raised and the water discharged. 



After the screw-cap has been uncoupled the cup is automatic in its 

 working, and it is only necessary to clamp it on the line with the spring 

 clamp Y. Before paying out the propeller may be screwed up to its 

 full extent, but this is not necessary. 



As the cup descends the resistance of the water raises the valves, 

 and also screws up the propeller until the lower thread in the hub clears 

 the upper thread on the shaft, when the propeller uncouples and revolves 

 freely on the shaft, where it is guided at top and bottom, which pre- 

 vents chafe on the thread. 



Should a stoppage then be made to fasten on another cup, the pro- 

 peller will not screw down by the I'olling or pitching of the vessel. 



It will be noticed that the blades are bent on their upper edge. With 

 the 43lades thus bent, and the propeller made very light, it has been 

 found, experimentally, that by rising and falling equal distances through 

 the water the propeller will screw up instead of down. Without bonding 

 the propeller blades, it is evident that the propeller would gradually screw 

 down by a rising and falling motion, since its weight would assist its 

 screwing down and resist its screwing up ; but, even thus, experiments 

 have shown that for an alternating motion through the water, continued 

 for a longer time than any probable stoppage, the propeller would screw 

 down only about a quarter of an inch, which is much within the margin 

 of safety ; and, on relowering, the propeller, in that case, would again 

 rise and uncoui)le. However, the bending of the blades overcomes any 

 bad effects from the motion of the vessel, and the valves are free to 

 open during the whole descent without regard to the number of stop- 

 pages made. 



At any stoppage each cup has within its cylinder a specimen of the 

 water from the place where it stops. 



On hauling in, the propeller of each cup screws down, by the resist- 

 ance of the water, until the upper thread of the hub clears the lower 

 thread of the corresponding screw on the shaft, when the propeller drops 

 on the screw-cap, — which until that time has been at rest, — the lugs 

 Ii', R clutch into the slots U, U, and the screw-cap is screwed down until 

 it touches the upper valve, wliich keeps both valves closed. It is evident 



