Mr. Patten’s 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 remarked, 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. | 
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 ad Colladon have re- 
ferred it, to percussion. 
Art. XVII.—Mr. Parren’s Air Pump. 
To the Editor of the American Journal of Science, &c. 
Sir, 
I DEEPLY 7 that the remarks which were offered on 
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 offered. I can 
truly state, what was before explicitly stated in the remarks, 
that I referred to the subject, “‘ not as claiming credit” for 
the invention, 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 | hoped to dispense with valves, and by 
i 
ie 
3 
M. Silliman then explains the effect, as many others have 
