254 Dr. Turner's Remarks on 



expansion and contraction of their distances must be ijimilar 

 to those of the leaden balls. 



Thus, if we suppose A and B to be two particles of atmo- 

 spheric air, at the distance they are in the atmosphere; if 

 they be compressed as at C and D, and suddenly released, 

 they will be separated as at E and F, and produce all the 

 effects of a corresponding rarefaction or dilatation. It is true 

 they may not separate so far as at E and F, because of the 

 interruption they meet with from other particles of air in the 

 atmosphere ; but it is reasonable to conclude that they will 

 separate beyond the distance of A and B. After being se- 

 parated to their greatest distance, they will collapse, not by 

 the reaction of the elastic force between them, as in the case 

 of the leaden balls, but the similar action of the elastic force 

 of the particles of air into which they are projected. 



In this view of the phaenomena, by the combined mechani- 

 cal action of elasticity and momentum, the low pressure of 

 highly compressed steam, at the place where it is released, 

 becomes only what is due to its mechanical dilatation, — the 

 consequence of its previous compression. And, accordingly, 

 it is found that the more it is compressed, the more dilated 

 and the colder it is when suddenly released. 



XXXIX. Remarks on Mr. Phillips's Essay on Manganese:— in 

 a Letter to the Author. By Edward Turner, M.D. F.R.S.E. 

 8^0. Professor of Chemistry in the University of London*. 



My dear Sir, 

 IITAVING the misfortune to differ from you respecting se- 

 •'■-*- veral of the remarks contained in your Essay f on a new 

 ore of manganese, and feeling that the temperate discussion 

 of scientific subjects rarely fails to advance the interests of 

 science, I do not hesitate to offer the following comment on 

 your opinions. As you now admit the accuracy of my view 

 relative to the formation of the protosulphate by the action of 

 sulphuric acid on the peroxide of manganese, I need not par- 

 ticularly advert to that subject ; but will confine my remarks 

 to two parts of your Essay : namely, to your description of the 

 Warwickshire manganese, and to your observations on my 

 analysis of manganite. 



I. I cannot admit the correctness of your views on the com- 

 position of the Warwickshire manganese ; and the opinion 



• Communicated by the Author. 



t Last Number of this Journal, page 209. 



which 



