DEEP-SEA EXPLORATION. 
341 
With the screw cap np .and the xiropeller in .any position, the cnp i.s .automatic, and may, if 
desired, be lowered into the w.ater with no other preparation; yet it is a good practice first to screw 
np the propeller hy h.and to observe if the threads are in perfect working order. Assuming tlie 
propeller is to be low down on the shaft, or even resting upon the screw cap, the action of the water 
is as follows : 
As it descends, the valves are lifted and held up by the resistance of the water; by the same 
agency the propeller is revolved and carried upward until, like the screw caji, it is uncoupled, after 
which it revolves freely on the shaft, impinging .against the German-silver sleeve i. If the propeller 
hub is allowed to come in contact with the sleeve while the screw threads are still engaged, it may 
remain impacted during the subsequent ascent. To insure uncoupling at the proper time the guide 
cap, which fits over the top of the hub, must be set well home in its position, when the propeller is 
fitted to its shaft. It will be noticed that the blades of the propeller are bent along their upper 
edges. With the blades thus bent, and all x)arts of the propeller made very light in weight, it has 
been found experimentally that the .alternating movement of translation imparted to the submerged 
cu]> by the vessel’s motion in a seaway will cause the jiroiieller, when engaged with the threads on the 
shaft, gradually to screw up rather than d.own. This shows that stoppages in the descent, whether to 
.attach addition.al cups to the rope or wire, or for any purpose whatever, may be made with safety if 
the vessel is kept idle in the water, that is, without headway or steruboai-d. Were the blades not bent 
it is evident that the proi>eller would gradually screw down by the same alternating movement, 
since its weight would assist its action in screwing down, but resist the opposite motion. Even thus 
experiments have shown that with the alternating movement continued for a longer time than 
would jirobaljly be occupied by any stoppage, the projieller would screw down on the shaft only a sm.all 
proportion of the distance to the screw caj). It is plain that in the event of such action the propeller 
would rise and uncouple each time the descent was continued. However, the bending of the blades 
insures safety, and the valves are left free to open during the whole descent. At any stoppage in 
the descent e.ach cup cont.ains within its cylinder a specimen of the water from its locality at the time 
being, allowing a margin of 1 or 2 feet. 
As soon as the ascent is begun, the valves of each cu]) are pressed firmly on their seats by the 
resistance of the water, and each propeller begins to screw down along its shaft under the same 
iulluence. When the upper thread inside the hub of the propeller clears the lower corresponding 
thread on the shaft, the propeller uncouples and drops uiion the screw cax5, which it clutches. The 
screw caj) is then carried down until it comes in contact with the upper valve, from which position it 
can not be removed by the action of the water or of the propeller. Both valves being thus locked, 
stoppages may be made thereafter during the ascent without risking the identity of the inclosed 
specimen of water. 
The distiince through which the cup must pass, in order that the propeller may traverse the sh.ift 
and lock the valves, may be varied liy altering the pitch of the propeller. As shown in the drawing 
the propeller would probably not perform its work short of 50 fathoms. I settled on about 25 fathoms 
as the distance most convenient. With this distance it would not be prudent to require the uppermost 
cup to bring a specimen from ne.arer the surface than 50 fathoms. If the propellers were .arranged to 
lock the valve in an ascent of about 25 fathoms, .and the uppermo.st cup were lowered only to .a depth 
of 10 fathoms, for instance, obviously when that cup had arrived at the height of the vessel’s deck 
the submerged cups, having passed through <a distance of only about 12 fathoms, would not have 
become looked. Each cup, as soon as discharged, should be thoroughly rinsed in fresh water. 
We have found these bottles to work satisfactorily for the iiiirpose of collecting 
water specimens for specihc-gravity determinations; Init they will not retain the gases, 
and are therefore not available for collecting specimens for chemical analysis. 
Experience has taught that it is advisable to reset the valves whenever the 
bottles are to be used, as their adjustment is liable to be impaired in releasing the 
screw cap from contact with the upper valve. Although Sigsbee states in the remarks 
quoted that the iipiier valve seat is detachable for purposes of cleaning, we hud in 
practice that the accumulation of verdigris on the screw threads makes its safe removal 
impracticable. The valves and valve seats can be readily cleaned, however, without 
detaching the upper valve seat. 
