his Hi/grometrical Researches made hy Dr. Hudson. 189 



air, I subsequenlly informed him that, as is obviously the case, 

 tlie ratio between the depression in dry and the difference be- 

 tween it and the depression in moist air is expressed generally 

 by the following proportion : 



D:D-rf: :/-:/- -/'+/", 

 f and f representing the respective forces of vapour at the 

 temperatures shown in each instance by the wet thermometer. 

 I have now arrived at my first ground of complaint against 

 Dr. Hudson. In a postscript to his paper in the Philosophical 

 Magazine for October 183.5, he represents me as communi- 

 cating to him on the occasion just mentioned, the proportion 

 T): d: :/' —f -\- J", that is, he omits D from the second 

 term, and then proceeds to comment upon an absurdity 

 created by himself*. 



As far then as relates to my first paper, I have merely to 

 recapitulate the following facts. My formula is in itself com- 

 plete, and immediately applicable in practice; Dr. Hudson's 

 is useless without a knowledge of the value of D. My formula 

 was communicated to the Royal Irish Academy, and explained 

 in his presence a full year before the publication o^ his method. 

 Lastly, his fundamental proportion is but a particular and 

 very obvious case of my general expression, as has been al- 

 ready demonstrated. 



If under such circumstances I were to maintain that Dr. 

 Hudson borrowed his method from me, I think it will be 

 admitted I shoukl be able to establish a very probable case 

 against him. Such a charge, however, I have never advanced 

 either by the method of direct assertion or oblique insinua- 

 tion, and I am even now prepared to admit that Dr. Hudson 

 may have arrived at his proportions previous to any knowledge 

 of my hygrometric formula. Has Dr. Hudson treated me with 

 the same degree of candour? This point the reader will be 

 better able to decide after perusing the following statement. 



At a general meeting of the Royal Irish Academy, held in 

 April 1335, I communicated a second paperf, the object of 



* If I had to do with any other person I should have no hesitation 

 in concluding that, writing in the liurry of business, and what I never 

 dreamt would meet the public eye, I had myself been the author of 

 the omission in question. The charge, however, I have preferred against 

 Dr. Hudson I cannot abandon without replacing it by one of nearly 

 equal gravity. Dr. Hudson has persisted in attempting to fasten upon me 

 tlic proportion D: d '■'■/'■/ —f +/"» and without the slightest allu- 

 sion to the fact of my having complained of being niisrejjresented on this 

 very point, and demonstrated step by step in his presence the manner of 

 deducing the correct proportion ironi n)y own formula. 



f This paper is to be found in the Numbers of the Philosopiiical Maga- 

 zine for October, November, and December, 1835. 



