Narrative ok Bahama Expedition. 13 



bottom. The angle in the bar, however, is rather a disadv^an- 

 tage than otherwise, as it seems prone to cause the affair to 

 become securel}^ wedged in between rocks, in which case a 

 tangle will foul quite as badly as a dredge. It is advisable to 

 provide a considerable number of extra tangle bars and a 

 quantity of suitable rope for the tangles, as the bars will often 

 be lost, in spite of every precaution, and the tangles will wear 

 out every two or three days, and have to be renewed. We 

 were advised to use old Italian hemp rope, and were told that 

 it made much more effective tangles than new rope. In 

 practice, however, we did not find any very perceptible differ- 

 ence, a fortunate thing for us, as the supply of old rope taken 

 was not suflicient for us to do our actual work. 



Our sounding line was two hundred fathoms in length, 

 twelve thread, furnished by the Gloucester Net and Twine 

 Company, of Boston, Massachusetts. Not expecting to dredge 

 below one hundred fathoms, we thought this sufficient. In 

 fact, however, much of our work was done in water nearer 

 two hundred than one hundred fathoms, and we found our 

 line of little use. Soundings made by hand at such depths are 

 at best unreliable, owing to the currents and drift of the 

 vessel. Hence we were forced to depend largely on the 

 charts to estimate the depth before putting over the dredge, 

 which itself proved more reliable in indicating the depth than 

 did our sounding line. Our experience indicates that sound- 

 ing at any considerable depth cannot be managed with accu- 

 racy with an old-fashioned line and lead. Piano wire and 

 detachable sinkers are now used in all deep-sea work. 

 Another device which is used on many steamers records the 

 depth by barometric pressure, and can be used when the 

 vessel is under full headway. I do not know whether or not 

 this method has been used for very deep soundings. 



For dredging it is necessary to provide some device for 

 carrying the iron rope over the bulwarks without friction, 

 and hoisting the dredge high enough to clear the side of the 

 vessel. This was effected b}^ stepping a dredging spar to 

 the foremast above the galley, so that it would swing aft of 



