116 Mr. R. Moon on the Theory of 



faithful to the evidence of their own senses and to their own un- 

 derstandings as not to be unduly influenced by the truth as it 

 appears to this man or to that, but who, with a singleness of 

 purpose which is regardless of all consequences, seek to behold 

 the truth only as it is in nature. 



[Our correspondent's concluding paragraphs (222, 225) have in- 

 duced us to publish his statements regarding the transmutable nature 

 of water, although we do not agree with him, and believe that the 

 results of his experiments will bear a very different interpretation . We 

 are of opinion that the supposed conversion of water into oxygen or 

 hydrogen (197 et seq.) is simply a decomposition of water, the oxygen 

 being evolved in the one pool, the hydrogen in the other, the earth 

 acting as the conductor between the two pools. The large surface of 

 the conducting wire in the one pool would naturally make the amount 

 of gas evolved at that pole appear very small. We also think that 

 the conversion of hydrogen or oxygen into water admits of a different 

 explanation ; it seems to us that the author has simply formed a gas 

 battery.— W. F.] 



XV. On the Theory of Pressure in Fluids. By R. Moon, M.A., 



Honorary Fellow of Queen's College, Cambridge*. 



IN a former papert I treated of four cases of pressure, in the 

 first of which the received theory as to the law of pressure 

 in elastic fluids was shown to contradict a universally received 

 principle, viz. the principle that action and reaction are espial 

 and opposite. In the second case considered, the assumption of 

 the truth of the same law was shown to lead to an absurd result ; 

 while in the two remaining cases the same assumption was shown 

 to lead to results which are palpably erroneous. 



If we inquire into the evidence upon which the received law 

 of pressure in elastic fluids rests, it will, I think, be found that 

 the law having been proved experimentally to hold in the case of 

 equilibrium, it was assumed, in the absence of any obvious reason 

 to the contrary, to hold generally ; and certain illustrious ana- 

 lysts having shown that its adoption led to some striking and 

 beautiful results, suspicion was lulled, and acquiescence in the 

 correctness of the theory became general. 



The cases considered in my former paper establish conclusively 

 that the law which has thus been assumed is not universally true. 

 A further inquiry into the subject therefore becomes necessary; 

 and such an inquiry, so far as the case of motion in one direction 

 is concerned, I propose to institute in the present paper. It will 

 be found, if I mistake not, to lead to conclusions of the greatest 

 interest, simplicity, and value. 



* Communicated by the Author. 



t See Philosophical Magazine, vol. xxxvi. p. 2/. 



