346 POPULAR LECTURES AND ADDRESSES. 



bottom. This of course very much lightens the 

 pull in hauling in the wire. By those means the 

 strengthening of the wheel and the lightening of 

 the pull the Americans got over the difficulty 

 very well. I, however, did not consider it desir- 

 able to throw away 30 Ibs. or 35lbs. of lead at every 

 sounding, as I believed I could modify the appara- 

 tus so as to make it easy to bring up the sinker 

 from any depth not exceeding 3,000 or 3,500 

 fathoms in ordinarily favourable circumstances ; 

 and I wished to reserve the expedient of de- 

 taching the weight for greater depths or less 

 favourable circumstances. In case of very 

 great depths. 4,000 fathoms or more, it will 

 probably be desirable to use a heavier sinker, 

 say 100 Ibs., and a trigger apparatus for 

 detaching it when it reaches the bottom. But 

 for depths not exceeding 3,000 fathoms, I 

 prefer generally a 30 Ib. or 35 Ib. sinker, with 

 no detaching apparatus. 



The way in which I have got over the diffi- 

 culty of saving the main sounding wheel from 

 destruction or damage by the pressure of the 



