4o him also before tlie Council; he stated that" he had not kept them ;" as 

 I had not retained copies of my own letters, I inclosed a statement of tacts, 

 with Dr. Apjohn's letters, to the Secretary (the Rev. Dr. Singer), in a sealed 

 parcel which was subsequently returned unopened, the Council having re- 

 solved that it was not expedient that scientific bodies should attempt to de- 

 cide on claims of priority on scientific subjects ; under these circumstances 

 I had no course left for my vindication among the members, but to print 

 the letters for the purpose of enabling tliem to judge for themselves ; 

 and as Dr. Apjohn has now removed the discussion from the limits of 

 the Academy to the far wider field of your valuable Journal, I feel equally 

 called on to put your readers in possession of the real facts of the case as 

 proved by Dr. Apjohn's own letters. With respect to the complaint of my 

 having published Dr. Apjohn's letters, I may repeat that Dr.Apjohn and I, up 

 to the period of that correspondence, never had any intercourse, that the cor- 

 respondence related solely to the subject of the moist bulb hygrometer, that 

 it contained nothing private or confidential, and that Dr. Apjohn himself 

 created the necessity for my producing his letters, by wholly denying my claim. 

 With regard to Dr. Apjohn's charge (p. IS9 of your last Number [Sep- 

 tember 1836]) that I had " created an absurdity in his formula for the pur- 

 pose of commenting on it," or else that I "continued to misrepresent him 

 after he had complained of my havingperverted his formula;" in reply, I give 

 the following extract from Dr. Apjohn's letter to me on the subject : 



" 19th February, 1835. " 

 <<«•««« J ^jjj sorry to be obhged to confess, that I may have led 

 you somewhat astray by a communication I made to you at the commencement 

 of our correspondence. I stated, I believe, that your proportion for arriving at 

 the dew-point was a consequence of ray formula ; upon however looking at the 

 matter again, I find that such is not the case. If D ~ =depression in dry and d 

 in moist air, /~ the elastic force of vapour at the stationary temperature of the 

 hygrometer in dry, and/' in the moist air, and/" the elastic force of vapour at 

 the dew-point of the latter, then by my formula I can show that D : d : :/~ :/" 

 + f~ — /'. I was led to the erroneous result which I imparted to you, by con- 

 founding /—with/', quantities which are quite distinct." 



The above sufficiently shows that the absurdity was not of my creation. 

 Dr. Apjohn undoubtedly complained that I had given an erroneous formula 

 as his, but he did not enter into particulars, as he states he did; I have now, 

 indeed, no doubt that it was his intention to particularize, and that he be- 

 lieves that he did so. I then conceived, however, that his complaint refer- 

 red to the formula I gave as his (corrected) in the note, p. 259, vol. vii. of 

 your Journal, and replied thereto. The extract from his letter shows also 

 that 1 had an ample answer to his first charge, and consequently (if, even, 

 I were capable of such a thing,) could have no object in affecting to misun- 

 derstand the formula to which he really intended to allude. It maybe sup- 

 posed that the error in the letter merely arose from the accidental omission 

 of D in the second term of the formula ^but is the context reconcilcable with 

 the explanation given by Dr. Apjohn on this a.ssumption ? He now says 

 that having found that my proportion of D : D —d : :/' :/" was only true 

 in the particular case to which I applied it ; he sent me the other more gene- 

 ralformula D : D —d : :/~:/~ — /' +/" ^^ embracingthe former. But 

 what says his letter? that he has found that " the former proportion is not 

 a consequence of his formulay This needs no comment. 



Dr. Apjohn has stated positively (see p. 191,) that he " had resolved to 

 employ all these methods of experimenting before 1 commenced that cor- 

 respondence with him." In support of this he has adduced no evidence e.\- 



