i$0 Miscellaneous Intelligence. 



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 composed of 4 copper, 1 tin ; 

 but this hard 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 it ; but when gravers were made 

 of alloys, all harder than copper but softer than steel, the copper 

 wheel immediately attacked them. Hence it appears that a small 

 diflerence in the hardness of bodies requires for its compensa- 

 tion a much greater one in the velocities. It is remarkable, that 

 though files 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 sub- 

 stances that were attacked by the wheel. The authors conclude 

 by stating their opinion, that the experiments are sufficient to prove 

 the dependence of the effect upon mere percussion, and that the 

 softening of the steel is an accidental circumstance. 



Professor Siiliraan, on the same subject, remarks, that the effect 

 in question was first described by the Rev. H. Daggett, and was 

 discovered by some mechanists belonging to the sect of shakers. 

 The thinner the pieces of steel the more rapid the effect: when not 

 thicker than a common joiner's saw they were cut almost as rapidly 

 as wood is cut by the saw itself It is remarked also, that none 

 of the ordinary operations commenced upon cold and hard steel 

 will divide it with so much rapidity as this mode of applying soft 

 iron. 



M. Silliman then explains the effect as many others have done, 

 by considering the steel as previously heated and softened and then 

 cut ; but he observes that it is not " perfectly clear why even ignited 

 $teel should be so easily cut by the impinging of soft iron. No 

 smith probably ever thought of attempting to divide steel by ap- 

 plying an iron tool ;" so that whether the steel be considered as hot 

 or cold the effect may be referred, as MM. Darier and CoUadon 

 ha\e referred it, to percussion, 



2. Velocity of Sound. — Results deduced by Dr. Gregory from the 

 experiments made by himself and others on the velocity of sound. 

 Cambridge Phil. Transactions, 1824. 



i. That sound moves uniformly ; at least in a horizontal direction, 

 or one that does not greatly deviate from horizontality. 



ii. That the difference in the intensity of a sound make no a - 

 preciable difference in its velocity. 



