488 TUP: APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



engines. Among the interesting applications of this mechanical power 

 we must mention the thousand operations employed in making the 

 engines themselves, especially the forging of large metal pieces. The 

 instrument which serves this purpose is the steam-hammer on which 

 we may give a few details. 



The steam-hammer is, so to speak, a peculiar kind of steam- 

 engine in which the force is directly employed to produce the motion 

 of the instrument. Among the largest steam-hammers in existence 

 those at Woolwich and in Krupp's famous works in Germany may be 

 mentioned. 



The steam-hammer which has contributed so much to develop the 

 manufacture of iron, that chief material of modern machinery and 

 industry, was invented by Mr. Nasmyth. 1 These gigantic hammers, 

 which are employed in all the factories where iron or steel are forged 

 in great masses, do not receive their motion from a steam-engine, 

 but the steam directly raises or lowers them between two enormous 

 uprights of cast-iron which serve as guides to their motion. 



Fig. 328 shows how the hammer works. Imagine an iron monkey 

 whose weight is fifteen tons moving itself between two uprights or 

 slide-bars, suspended to the strong piston-rod of the cylinder into 

 which the steam can penetrate at pleasure. This steam arrives by 

 the pipe V, 'and thence by the port opened at the base of the pump 

 beneath the piston, which is then driven upwards by the elastic force 

 of the fluid. By means of a lever L, a rod T is acted on which 

 lowers a lateral slide-valve, and the steam escapes into the air by a 

 chimney UE. The steam acts here by a single expansion, but steam- 

 hammers are constructed in which it serves both to raise the enor- 

 mous weight, and to precipitate it downwards. M. Turgan, in his 

 work, Les Grands Usincs, refers to an enormous steam-hammer con- 

 structed at Kirkstall near Leeds, for the Victoria Eailway Company 

 in Australia. This hammer is either single acting or double-act- 

 ing, thus the steam acts in both directions, that is to say, it can 

 alternately raise the hammer, and enter above it to quicken its descent, 

 and to augment in consequence the action of its weight. This 

 arrangement, which gives the power of multiplying the number of 

 blows in a given time, is specially advantageous in forging pieces of 



1 In the French edition the invention is ascribed to M. Bourdon, of Creuzot. 



