The introduction of the double bottom for water ballast in ships, brought about a great increase in the amount of necessary punching caused by the numerous man-holes required through the floors and longitudinals. These man-holes, oval in shape as shown by Fig. 1—of say 18-ins. by 12-ins.—had to be punched all round by the rivet-punch, and the edges afterwards dressed by hand with a chisel. To economise work in this connection, need was felt for a machine which would be capable of punching a man-hole of the ordinary size out of the thickest plate at one operation. In 1879, at the request of one of the prominent Clyde firms, Messrs Craig & Donald, the well-known machine-tool makers of Johnstone, introduced a man-hole punching machine which cut holes 18-ins. by 12-ins. at the rate of seven per minute, in such a way that no after-dressing with chisels was required. This machine, an ordinary eccentric motion one driven by its own engine, although tested and found capable of cutting an 18-in. by 12-in. hole through a plate 1-in. thick, was superseded in the yard for which it was made, by another, designed to meet the requirements of the heaviest type of vessels built on the cellular principle. This machine—also made by Messrs Craig & Donald, and five or six of which are now at work in yards on the Clyde and at Barrow—was capable of piercing a hole 30-ins. by 21-ins. through a plate ¾-ins. thick, at one operation, and was actuated by hydraulic power. The ordinary eccentric machine, driven by engine attached, is still in favour for lighter work, and machines of this type are at work in several of the East Coast yards capable of punching holes up to 21-ins. by 15-ins. through plates ¾-ins. thick. Reverting to the subject of the proportion of material requiring to be heated before manipulation, it is noteworthy that the employment of mild steel is a source of economy in this connection as well as in the many others already noticed. The superior homogeneity and great ductility of the material favours cold-bending when such an operation would be fatal to iron. Not only does an economy in labour result, but incidentally there is a further advantage. Cold-bending distresses steel less than hot-bending, and the special precautions so often taken, in the way of annealing, to toughen steel which has been operated upon when hot, are thus obviated.