JoLY — On the Investigation of the Deep-sea Deposits. 265 



•easily calculated. The effect of the lifting of the ship on a swell is only to 

 increase the submergence of the float. In this manner a stress may be applied 

 which cannot exceed a certain calculated amount, and cannot vary abruptly. 

 When the drill is released, the beliaviour of the float indicates the fact, as it 

 will not then be submerged by hauling in the rope. 



Although the pull from tlie ship is by this arrangement reduced to one- 

 half the lifting force, it might be that even this amount of winch-power was 

 not available when the extraction of the drill was involved ; for it is desirable 



that a considerable force be at command for this purpose. I refer now 

 especially to operations carried out on a small boat. A simple mode of 

 raising the drill may, however, be resorted to, which has at once the advantage 

 of being adequate and of guarding against suddenly applied stresses. A 

 nipper as before is let down a few fathoms on the lifting wire, and then 

 locked. To tlie nipper a block- and-sheave is attached in the manner already 

 described. A rope as before passes under the sheave. One end of it is on 

 board ; the other is made fast to a strong waterproofed canvas bag of 

 cylindrical or balloon shape. This bag is hauled beneath the surface, and is 

 kept from sinking by a little contained air. The mouth of the bag is 

 inverted, and a rubber tube leading from the boat enters the bag from 

 beneath. A foot-blowers is now used to increase the volume of air in the 

 bag ; and this increase is continued till the drill is released. A little 

 calculation shows that this method presents no difficulties as regards the 



