38 TRANSACTION OF THE 



of the increasing strain wliicb it has to bear in passing around the several 

 sheaves when it is being payed out, -with the maximum strain, and thus 

 greatl}' diminish or perhaps entirely obviate the slipping of the cable on ail 

 the sheaves." 



We may add that \fe see no reason why this apparatus should not also be 

 used for hauling in the cable when necessary^ if sufficient engine power be 

 provided for that purpose. 



The most important consideration, however, to which we have directetl 

 our attention is, how to guard against the strain being brought on the 

 cable while paying out, greater than it is considered capable of bearing 

 without a risk of damage ; that is, having determined the maximum strain, 

 how to counteract the numerous causes which have a tendency to increase 

 it, and which, especially when brought into operation simultaHeously, would 

 otherwise endanger or destroy the cable. 



The means which we recommend for this purpose are, the substitution 

 for the present brakes of the others, moving with the same regular velo- 

 city, but of twice the diameter, and having their rubbing surface of gun 

 metal about 12 inches wide, each brake being capable of doing the wh(i>le 

 work, but both may be in operation together, if found convenient. They 

 should be constructed on the plan patented some years ago by Mr. Appold. 

 Their rims should be lined with strips of lignum vitje, about three inches 

 broad, and half an inch apart, and immersed about one-third of their diam- 

 eter in cisterns of salt water, it being found by experience that brass and 

 lignum vitfe work together under great pressure with no appreciable wear. 

 Mr. Appold's brake has the advantage of insuring a uniform holding power, 

 so long as the pressure on the lever remains unaltered, capable of being 

 increased or diminished to any required degree with certainty. 



A slight movable sheave of the same size as those on the paying out ap- 

 paratus should be introduced, and be arranged to move horizontally on the 

 deck, through a space of about 20 feet, by the action of strong springs of 

 vulcanized India rubber. The cable, by passing over that on the stern of 

 the ship, would be relieved from the great irregularities of strain to which 

 it would otherwise be subject, and the position of this sheave would at all 

 times be the surest indication of the maximum strain on the cable, a mat- 

 ter of the utmost importance to be known, as upon it should depend the 

 adjustment of the brakes and other operations for insuring the safety of 

 the cable itself. 



The importance of carrying these principles into operation is enhanced 

 in our niinds by our conviction that any injury sustained bv the cable in 

 deep water would probably be irrepa'-able, it being exceedingly doubtful 

 whether the cahle could by any contrivance be safely arrested, if broken 

 while running out, or raised from the bottom of the sea. 



As an additional means of obviating the danger of breaking the cable, 

 we recommend the adoption of some kind of compensating arrangement to 

 allow for the rise and full of the stern of the ship in a sea-way, which may 

 be controlled either by springs or weights. We have seen at Mr. Hodges, 



