:')2(i Jlction of Iron in motion on Temftered Steel. 



of the iron also on it seemed rather diminished than other- 

 wise. 



Hence MM. Daricr and Colladon conclude that the effect 

 was not due to the softening of the steel ; nor, as the wheel 

 Was clean, could it be due to the particles of steel adhering 

 to its surface ; and they feel inclined to attribute it to the 

 blow only, thinking it easy to conceive that the fragile steel 

 may be broken by the action of the iron before it can have 

 time to introduce itself between its molecules. 



Rock crystal and agate were held to a wheel of soft iron, 

 moving at velocities from 130 to 200 feet per second: the 

 first was acted upon, but the surface produced was unequal 

 and rough; the agate was also acted upon though less power- 

 fully : but it is supposed that this means, even when much 

 greater velocities are used, cannot be applied to the cutting 

 of these or similar substances with advantage ; at the same 

 time the elFects, though small, conlirm the authors in their 

 view of tlic cause of the phenomenon. 



They then quote similar eirects known to be due to the 

 force of percussion, as the piercing of a plank by a ball of 

 tallow, the force of liquids, even when moving with great 

 velocity : when, therefore, to an edge of soft iron, moving 

 with the velocity described, hard elastic bodies are applied, 

 as steel, agate, &:c,, their particles are displaced and torn off, 

 for they cannot move by each other without division ; but 

 when a soft body is applied to the wheel, as copper, brass, 

 tin, and even soft steel, then the substance is pressed before 

 the iron, and being ductile rises up in burs 



The iron wheel was replaced by one eomposeo of 4 cop- 

 per, 1 tin ; but this liard and elastic alloy slipped over the 

 bodies presented to it without producing any effect except 

 violent vibrations. A wheel of copper was then used ; steel 

 gravers constantly cut this wheel without being touched by iti 

 but when gravers w^ero made of alloys, all harder than cop- 

 per but softer than steel, the copper wheel immediately at- 

 tacked them. Hence it appears that a small difference in 

 the hardness of bodies requires for its compensation a much 

 greater one in th<i velocities. It is remarkable, that though 

 fdes and springs of steel were applied forcibly^ for a long 

 time, to the copper wheel, moving with extreme rapidity, 

 scarcely any heat was produced ; and the same was the case 

 with the substances that were attacked by the wheel. The 

 authors Conclude by stating their opinion, that the experi- 



