Mr» Patients Air Pump. 327 



ments are sufficient to prove the dependence of the effect 

 upon mere percussion, and that the softening of the steel is 

 an accidental circumstance. 



Professor Silliman, 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 it- 

 self. It is remark<jd, also, that none of the ordinary opera- 

 tions, 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 " per- 

 fectly clear why even ignited steel should be so easily cut by 

 the impinging of soft iron. No smith probably ever thought 

 of attempting to divide steel by applying an iron tool ;" so 

 that, whether the steel be considered as hot or cold, the ef- 

 fect may be referred, as MM. Darier and Colladon have re- 

 ferred it, to percussion. 



Art. XVII. — Mr. Patten's Air Pump. 



To the Editor of the American Journal of Science, &c. 

 Sir, 



I DKt'PLY regret that the remarks which were ollered ou 

 Mr. Patten's Air Pump, in a preceding number of your 

 Journal, should have excited any jealousy, or have produced 

 that degree of feeling, which appears to be evinced in Mr. 

 P.'s animadversions upon those remarks, and which differ 

 so much from the spirit in which they were olFercd. I can 

 truly state, what was before explicitly stated in the remarks, 

 that I referred to the subject, " not as claiming credit" for 

 the invcjition, but to propose an improvement. There are 

 few men whose inventions, like those of Wollaston, are per- 

 fect at the moment of their production ; and I ventured to 

 suggest what I conceived to be an improvement of Mr P.'s 

 invention, by which 1 hoped to dispense with valves, and by 



