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XX. On Mr. Samuel Seaward's Claim to the Invention of 

 a Hydro-pneumatic Pump for compressing Gases, $c. By 

 Mr. John Martineau. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



J OBSERVE in your last Number a drawing and descrip- 

 tion of a pump for condensing gases, by Mr. S. Seaward, 

 which pump he states to be his invention. 



As far as I am myself concerned, I should have hardly thought 

 it worth while to contradict his statement; but I cannot in 

 justice to yourself allow your respectable Journal to be made 

 the vehicle for conveying a falsehood to the public. 



This pump was constructed at the manufactory of which I 

 am a proprietor, during the time that Mr. Seaward filled a 

 situation as draughtsman in it. In that capacity he made the 

 necessary drawings connected with it ; but I do most positively 

 assert, that he did not invent or suggest any one essential 

 part of it. 



I content myself with simply stating the above facts, 

 And remain 



Your most obedient servant, 

 City Road, Aug. 10, 1824. John Martineau. 



XXI. An Attempt to explain the Action of the Voltaic Pile. 

 By Mr. Thomas Pollock. 



T^HE power of the Voltaic pile as an instrument of che- 

 -*■ mical analysis is owing to the influence its action pro- 

 duces upon the radiant matter which common matter contains, 

 and to which its various forms are owing, and which, when 

 in motion produces heat. 



The action of the pile may be readily explained when one 

 fact is previously assented to, — that a radiant matter capable of 

 producing heat, when in motion, pervades all the matter, solid, 

 fluid and gaseous, of the universe; and that no motion whatever 

 can take place upon the surface of our globe without producing 

 a change in the distribution of this general pervading principle. 

 If a gas become a fluid, or a fluid a solid, there is a diminution 

 of capacity for heat; there is contraction of volume, and the 

 form this matter has now assumed, owing to contraction, de- 

 mands less of this general pervading principle, and heat is 

 presented to surrounding bodies. If this change take place 

 with rapidity, and bodies possessing a great capacity for heat, 

 Vol. 64. No. 816. Aug. IS24-. R as 



