104 Mr. R. Moon on the Law of Gaseous Pressure. 



out having fallen/' the conclusion arrived at simply does not 

 follow from the premises. 



If, on the other hand, by the above allegation is meant that a 

 body cannot move from a particular position unless it have pre- 

 viously acquired a certain velocity, the point to be proved is 

 simply taken for granted. 



If I have misunderstood the point of Mr. Strutt' s paradox, I 

 trust that he will set me right in regard to it ; and as he must 

 be well acquainted with the fallacy which it involves, he will 

 perhaps not object to state distinctly in what that fallacy consists. 



As to the paradox which I have brought forward, I contend 

 that its fallacy consists in the false assumption of the received 

 law of pressure. If Mr. Strutt is not satisfied with this expla- 

 nation, I must call upon him to state definitely the particular 

 point in which my reasoning is defective, instead of contenting 

 himself with a vague assertion of analogy, where, as I contend, 

 nothing of the kind exists. 



Mr. Strutt thinks I "must admit that it is remarkable that 

 so apparently reasonable a law should lead to such absurd con- 

 clusions." 



I view the matter in a totally different light. In any syste- 

 matic investigation of the subject which may be made in the 

 present state of our experimental knowledge, it appears to me 

 so much a matter of course to assume that the expression for the 

 pressure will contain both velocity and density, and the con- 

 trary supposition appears to me to be so opposed to every sound 

 principle, that the signal failure of the latter is exactly what I 

 should have expected. It was in fact this anticipation that led 

 me to the examination which ha^ resulted in the detection of 

 the cases of failure I have here and elsewhere adduced. With 

 the statement of one of them, of somewhat peculiar character, I 

 will conclude these remarks. 



In the last case, a vacuum being supposed to exist above the 

 piston, suppose that instead of an additional weight being intro- 

 duced the piston is suddenly removed at the time /, then at the 

 time t, the density^of the air being throughout unaltered, we 

 shall have according to the received law a finite pressure at the 

 highest point of the aerial mass ; i. e. we shall have a pressure 

 where nothing is pressed ! — a conclusion opposed alike to the dic- 

 tates of common sense and the significance of language. 



6 New Square, Lincoln's Inn, 

 January 6, 18/3. 



