TRANSACTIONS OF THE SECTIONS. 187 



On Chain-cable and Anchor Testing. By R, A. Peacock, C.E. 



1. To adjust the weights of the hydrostatic press, the author recommends an 

 instrument like a pair of pincers, 10 inches long from the pivot to the ends of the 

 long legs, and 1 inch from the pivot to the shorter ends ; and, gTasping- the 

 diameter of the indicator valve with the shorter ends, its amoiint will be rend off, 

 magnified tenfold, at the long ends with a scale and vernier, and there need be no 

 error exceeding ^^' ^^ th of an inch. Allowance should also be made for the friction 

 of the ram in the cylinder. Or, otherwise, provide a suitably strong coiled steel 

 spring with frame, nearly like a Salter's letter-balance, and graduate it up to 

 5 tons with actual tons of pig iron, then, on lajdng it on the platform in connexion 

 with the press, it will be known when the press is exei-tiug a force of 1, 2, 3, &c. 

 tons respectively, and the weights can be adjusted accordingly. Great weights will 

 be multiples of small ones. 



2. Nine different sizes of stud-link cables were tested at Woolwich, and 15'9 tons 

 per square inch was their average strength. But the average streng-th of ordi- 

 nary English iron is 25 tons ; so there is a loss of more than one-third of the 

 strength by making it into cables, which it is desirable to recover if possible. And 

 since there is tension on the exterior half and compression on the interior half of 

 the link, he proposes to heat the cables to cherry red before testing, which would 

 enable the particles to adjust themselves according to their respective tendencies 

 and take off the strain. And perhaps an advantage would be gained by cooling 

 them in oil. This annealing would probably make iron, of the same size, materials, 

 and make, homogeneous ; so that the degree of permanent elongation with the 

 Admiralty strain could be taken as a test of strength. 



3. He objects to the hammer test, because no two men vsdll strike blows of the 

 same force, and consequently no one can know the amount of that force. If any 

 blows are to be applied, he proposes to have a number of weights, each one as heavy 

 as a fathom of a different size of cable, and to let the proper one drop upon its cable 

 from one and the same height. 



4. He proposes to break one or more samples of each cable, and to state the 

 breaking force, or forces, on the certificates. 



5. An anchor is condemned when the testing strain causes a pennanent deflexion 

 of the arm of f inch by one set of rules and f inch by another set, without 

 anv reference to the length of the arm. He proposes instead to condemn all 

 anchors of which the permanent deflexion exceeds a certain fixed amount per foot 

 in length of the arm. 



6. Too much permanent set being justly considered fatal to the character of 

 a wrought-iron anchor, too much permanent set ought also to be fatal to the 

 character of a wrought-iron cable. 



On the Construction of Shot-proof Targets. By T. Symes Peideattx. 



According to the author's views, an armour-protected structure should consist 

 of two essentially distinct parts, a yielding face and a supporting back — the first, 

 a series of detached targets so fixed as to be capable of receding a certain distance 

 upon the impact of the projectile; the second, an inner self-supporting structure, 

 continuous throughout, and strong enough to sustain the weight and strain of the 

 detached targets suspended from it, and also to resist their pressm-e or support their 

 impact when receding before the blow of a projectile. 



On some of the Strains of Ships. 

 By Professor W. J. Maccitjoen Rankine, C.E., LL.D., F.B.S. 



In previous scientific investigations respecting the strains which ships have to 

 bear it has been usual to suppose the ship balanced on a point of rock, or supported 

 at the ends on two rocks. The strains which woidd thus be produced are far more 

 severe than any which have to be borne by a ship afloat. The author computes 

 the most severe straining actions which can take place in a ship afloat, viz. when 

 she is supported amidships on a wave-crest and di-y at the ends ; and he finds that 

 the bending action cannot exceed that due to the weight of the ship, with a lever- 



