On the Cutting of Steel by Soft Iron. 343 



which the parts of gun locks are made, were held against 

 the edge, of the revolving soft iron plate, they were imme- 

 diately cut by it, with a degree of rapidity, which was al- 

 ways considerable, but which was greater as the pieces of 

 steel were thinner. Pieces as thick as the plate of a com- 

 mon joiner's saw, were cut almost as rapidly, as wood is cut 

 by the saw itself Considered as an experiment, merely, 

 it is a very beautiful one, and in no degree exaggerated in 

 Mr. Daggett's account. There is a very vivid corruscation 

 of sparks, flying off in the direction of tangents, to the pe- 

 riphery of the cutting wheel, and an intense ignition of the 

 steel, extending for a considerable distance ahead of the sec- 

 tion, and on its sides, attends the operation. The impulse 

 against the steel, is so strong, that in several instances, it 

 was thrown against the opposite side of the room, with a 

 velocity that might not have been without danger to a per- 

 son standing in the way. It may be said, I believe, with 

 safety, that none of the ordinary mechanical operations 

 commenced upon cold and hard steel, will divide it with so 

 much rapidity, as this mode of applying soft iron. After all 

 it is evident that it is only a peculiar method of cutting red 

 hot, or possibly white hot steel, for the mechanical force 

 produces these degrees of heat, and it is one of the best 

 methods of evolving heat by mechanical impulse. The 

 steel of course loses its temper at the place of section, and 

 there only, for the softening extends but a little way and i& 

 limited to a narrow portion, marked 6y the iris colours, 

 known to be produced by heat upon steel. 



The iron plate, as Mr. Daggett states, becomes only warm, 

 and wears away, only very slowl);yei it does wear, for the 

 edges are left rough, and the channel of section in the steel, 

 exhibits, with a magnifier, minute striae or grooves, running in 

 the direction of the wheel's revolution. I know not that there 

 is any reason to suppose, any peculiar electrical phenome- 

 non, except that electricity always accompanies heat. It 

 is plain from the important use made of this mode of cut- 

 ting steeJ by the Shakers, and by Mr. Barnes, that it 

 may be of considerable practical importance. As a philo- 

 sophical experiment it is highly interesting, and it re- 

 mains yet to be shewn, why the heat evolved by the im- 

 pulse, should, nearly all be concentrated in the steel, and 

 be scarcely perceptible in the iron. Neither is it perfect- 



