JoLY — On the Investigation of the Deep-sea Deposits. 263 



freely upon it. Judging from the compressibilities ascertained for other 

 spirits, there would be little loss of buoyancy with increasing depth. The 

 float/, shown in Plate XX, is intended to be made of thin copper, and to be 

 buoyed with petrol. 



The form given to the body of the sounder is not without purpose. A 

 flat-bottomed vessel might adhere to the bottom by a "sucker" action, and 

 be brought up only with difficulty. Moreover, as designed, the sounder is 

 mud-tight. The tube permitting the passage of the drill rises from the 

 bottom without opening till it nearly meets the rotating collar. The drill is, 

 therefore, not likely to sink in soft mud if such existed at the surface of the 

 ooze. Tlie four projecting fins are for giving so much bite in the ooze as will 

 resist the reaction of the machine to the torque upon the drill. 



Experience only can decide as to what is best regarding the rate of working 

 of the engines and the weight placed on the drill. Experiments made upon a 

 small scale on a sample of globigerina ooze v^etted to the consistency of a 

 thick mud showed that above a certain velocity of spin an immersed vertical 

 cylinder experienced relatively little resistance to turning. Thus, a smooth 

 brass cylinder, immersed to a depth of 10 cms., and having a diameter of 

 2*6 cms., and urged round in one direction by a tangentially applied force 

 as given in the second column, rotated with the velocities given in the third 

 column. 



No. 

 1 

 2 

 3 

 4 

 5 



Biirface of mud free from water. 



Tangential force in grammes 

 200 

 300 

 400 

 500 

 600 

 600 



Revolutions per 



014 

 0-20 

 0-25 

 0-31 

 0-40 

 0-39 



Surface of mud flooded. 



7 . . 400 



8 , . 500 



9 . . 500 



10 . . 400 



11 . . 200 



12 . . 240 



13 . . 280 



14 . . 300 



PCIENT. PEOC. R.D.S., VOL. XIV., NO. XVIII. 



0-3 

 1-0 

 Very rapid. 



)j )> 

 0-31 

 0-50 

 2-0 

 Slow, changing to very 

 rapid. 



2t 



