HORIZONTAL iMOON, 



IV. 



235 



Examination of Mr. Ezektel Walker's Experiments and Theory of 

 the Enlargement of the Horizontal Moon. In a Letter from 

 C. L. 



To Mr. NICHOLSON. 

 SIR, 



A OUR correfpondent Mr. Ezekiel Walker, has favoured the Affertion of 

 world with a new attempt to account for the apparent enlarge- ^li^^^^^ 

 mentof the horizontal moon*, in which, afier indulging his images vaiy 

 wit, andexpreffing his aftoniaimcnt at-the expence of thofe ^^^^ ^^« P»P'^'» 

 who have laboured on the fame fubje6l, he proceeds to aHlire 

 us that the piStures on the retina are not permanent but vary as the 

 dimenfions of the pupil vary. 



That you, Mr. Nicholfon, who are in fome refpeft account- 

 able to the world for what you admit into your Journal, and 

 who poflefs a jufl: celebrity for the manner in which you have 

 executed the (a{k, — that you thould have omitted to favour the 

 writer and your readers fo far as to rejed his paper, is to me 

 no olherwife to be explained than by referring it to your im- 

 partiality ; which may have induced you to leave the refutation 

 of aiiedged fads to your correfpondents rather than enter into 

 a difcudion refpe6ling them yourfelf. 



I cannot for a moment fuppofe you to have had a doubt con- Confequences 



cerning this imaginary novelty in optics. If Mr. Walker's 5j5[7^^^^°Ji°'' 



pofition were true, the magnifying powers of the fame tele- founded. 



Ibope would vary with its aperture; a well illuminated theatre 



or room would become contra6led in its apparent dimenfions; 



the paper at which I now look would fuddenly become larger 



when I cover the candle with my hand ; and in a word we 



fliould have no certainty if the magnitudes of things were to 



appear different with every change of the pupil. 



None of thefe things do in fadt happen, and it feems almoin Experiments of 



' . Mr. "Walker 



trifling to infift upon them. Still IqU is it neceffary to have repeated. 



recourfe to lines and figures; but for the fake of your lefs 

 inftrucled readers I will meet Mr. Walker by corre6t experi- 

 ments of the fame defcription as his own, 



* Philof. Journal, IX. 164. 



JExp. 



