190 REPORT — 1865. 



being, as it appears to the writer, that each hemp fibre consists of a series of col- 

 lapsed tubes between knots, which, upon filling with water, straighten from knot 

 to knot, and therefore slightly augment the total length ; whereas the same fibre, 

 if wound spirally, will reduce the length of the spiral, in consequence of its increase 

 in diameter in filling with water. Proceeding from this consideration, hemp yarn 

 of little twist is used in the manufacture of this cable, the copper sheathing binding 

 the fibres sufficiently to continue their strength, and the result is that its length 

 remains practically the same upon being immersed. 



In drawing this paper to a conclusion, the writer feels that he has laid himself 

 open to the charge of partiality in favour of one particular covering, but his excuse 

 is that he could not have done otherwise without doing violence to his convictions, 

 which, however, are open to criticism. So much will, he thinks, be readily con- 

 ceded, that the failure of deep-sea cables has hitherto been mainly due to the 

 mechanical imperfections and perishable nature of the outer coverings. The un- 

 fortunate result of the last attempt to establish telegraphic communication with 

 America goes to strengthen this proposition. Both the insulated conductor and the 

 paying-out machinery had been prepared with extreme care ; the great ship was 

 well adapted to its important work, which in all human probability would have 

 been crowned by success but for the unfortunate injuries which the insulated 

 core received through insufficient protection. The recurrence of the same kind of 

 accident may perhaps be avoided by special care ; but there remain the dangers of 

 kinks at the bottom, through the untwisting of the rope while in suspension, and, 

 most of all, the question of durability to be disposed of. 



It has been maintained by some that the outer covering of deep-sea cables is 

 only of use for submerging the same, and that its decay at the tranquil bottom of 

 the ocean could not harm the insulation ; but such a proposition is disposed of by 

 experience, and it is natural to suppose that the sheathing must give way first in 

 such places where it rests upon a stone or gentle elevation of the ground (and is 

 most exposed to chemical action). Upon giving way, the cable will sink to take 

 new bearings and cause the unsupported insulated conductor to separate. It may, 

 on the other hand, be maintained that a permanent metallic sheathing is requisite 

 to ensure the success of deep-sea as well as shallow-sea cables. 



Description of a Patent Steam Pile-Dnver. By W. Sissons. 



In this machine the ram ("one ton in weight) falls twelve times in a minute, with 

 a 5-feet lift. The size of the bottom frame is only 7 feet 6 inches square, and it 

 occupies a smaller space than an ordinary hand-machine, and can be used in any 

 situation, on land or afloat, where the other can. It supplies a deficiency long felt, 

 viz. something more powerful and expeditious than hand-machines, and something 

 less ponderous and costly than those steam-machines hitherto brought out. Du- 

 ring the past six years fifty-four of them have been made ; seven are in use on the 

 Thames Embankment, and Mr. Brassey has five in operation in Galicia. 



On Warming, Lighting, and Ventilating the Birmingham Town Hall. 



By B. Smith. 



