190 Dr. Apjohn on certain Statements relative to 



which was to detail a series of experiments, the results of 

 which established, if I mistake not, the perfect accuracy of my 

 formula for the dew-point. Now, in reference to these experi- 

 ments Dr. Hudson, in a note to the paper of his already re- 

 ferred to, makes the following observations. " It may not be 

 improper to state here that I communicated the views con- 

 taineil in this paper to my friend Dr. Apjohn two or three 

 days after he communicated his method to the Royal Irish 

 Academy, and I have recently had the pleasure of learning 

 from him that he has employed both the methods of experi- 

 menting on dry air, and on air of a known dew-point (heated 

 artificially), with the view of testing and establishing his own 

 formula." It is here undoubtedly insinuated by Dr. Hudson, 

 that I borrowed from him my methods of experiment; but as 

 such was not directly affirmed, I did not at the time think 

 it necessary to publish a formal contradiction. Since that, 

 however, all doubts as to his real meaning have been removed ; 

 for both at the Royal Irish Academy, and subsequently in a 

 pamphlet which he has recently circulated on thesubject, he has 

 preferred a distinct charge of plagiarism against me, and he has 

 published in support of the charge, without even the formality 

 of asking my permission, some letters of mine written in reply 

 to those which I have already described myself as receiving 

 from him. From this charge, and some others upon which 

 I shall not comment here, as they have not appeared in the 

 pages of any scientific journal, I have, I think I may venture 

 to assert, fully vindicated myself in the judgement of the mem- 

 bers of the Royal Irish Academy, and shall now proceed to 

 set myself right with the readers of the Philosophical Magazine. 

 Having arrived at the solution of a physical question 

 deemed of sufficient importance by the British Association at 

 its meeting in York to be inserted in their list of Desiderata 

 in science, it will, I presume, be readily admitted that I felt 

 extremely anxious to test its truth by submitting it to the 

 touchstone of experiment. I was, however, at the time of 

 communicating my formula well aware, for reasons which I 

 have elsewhere stated, that this could not be satisfactorily 

 done by means of Daniell's instrument, and corresponding ob- 

 servations with a wet and dry thermometer; and felt therefore 

 convinced, at a very early period, of the necessity of resorting 

 to the other methods. Now three such are immediately pointed 



to by the formula itself. Thus, 1st, since/" =/'~ 87 ^ 35' 



30 



ify" = 0, i. c. if the air be destitute of vapour, d = Slf x — ; 



