. |i6 Remarks on the Enquiries of Dr. Herfchtl refptiling Light and Heat. 



VII. 



\ Further Remarks on the Enquiries of Dr. Herfchtl lefpeEling Light and Heat. In a Letter 



from Mr. Jens Leslie. 



To Mr. NICHOLSON. 

 SIR, 



London, Nov. 17, 1800. 



M 



Y lafl: Letter, was written under the perfuafion that your Journal for Ottober con- 

 tained, at leaft in fubftance, ihetukoleoi Dr. Hcrfchel's late experiments and conjedlures. 

 Had I forefeen that the fubjeft would be refumed in a future number, I ftiould certainly 

 have deferred my remarks until the recital was clofed. I now, therefore, feel myfelf reluc- 

 tantly compelled to reconfider the queftion, and to (late ftill farther difEculties, fhall I fay 

 fallacies, which prefs the fequel. In moft cafes, the toil of criticifm is miferable waftc of 

 time; in every cafe, it is equally painful and inglorious ; and in coming forward to attack 

 the folidity of fails and conclufions fan£lioned by high authority, I (hall probably, with 

 men of a certain clafs, incur the charge of tfertierity and prefumption. But fuch pruden- 

 tial confiderations I utterly difregard, being convinced that, on occafions like the prefent, 

 I may promote the caufe of genuine fcience as effeftually by dete£ling errors as by an- 

 nouncing pofitive difcoveries. Fortunately, I need not at this time engage in much elabo- 

 rate difcuffion. The obje£lions which I formerly urged fubfift in their full force, nor do I 

 find on recolleftion any material aflertion which I fliould defire to correft. 



The additional experirrtents which claim examination contain little indeed that can be 

 ftriftly called original. They are employed for the moft in afcertaining fadls which have 

 been long eftablifhed, or which are familiar to every perfori who has the fmalleft tinfturc 

 of fcience. The paper opens with a formality and apparent caution that might lead us to 

 expeft a chain of proofs fcarcely inferior to mathematical evidence. We are foon forcibly 

 reminded however, th^xfuch is not always the fureft road to truth ; and that the minute 

 fpirit of fubdivifion has prevailed moft in the dark ages, and in the barbarous departments 

 of literature, when fenfe and reafon were alike buried in the verbiage of fcholaftic fyllo- 

 gifms, definitions, and diftiniilions. To the myftic number /even, the child of judicial 

 aftrology, the Doftor bows with reverence. Light not only confifts in fcven primitive rays, 

 but each ray has feven properties ; and fo likewifc correfponding have the " rays of heat." 

 To mufter up precifely thofc feven analogous properties, however, required fome degree of 

 manaeement, fince one of them is to inform us, that the rays of light and thofe of heat 

 •' are liable to be fcattered on rough furfaces 5" an exprelFion which, if it has any meaning at 

 all, muft denote irregular refleftion, and therefore, to common apprehenfion at leaft, feems 

 comprized under a former head. The parallel fo nicely drawn between the vidble and invi-- 

 fible rays, changes, in the laft article, into a curious contraft, which aflerts, in defpite of 

 vulgar prejudices, that Light may not give Heat, and yet that Heat may compofe Light. 



Of 



