59© Second p^vidicationlpf Dr, lUrscheVs Theory , ^e, 



^ts really existed, bi^t wg^cQlourctJ freaks if such fijt^w^re 

 imaginary. Tbe experiment was most careFuily made, as 

 appears by tlie thirty- first articlcj and no symptoms what- 

 ever of such coloured streaks were perceivable. Hence 

 t!ie author considered it as an cxp^rimentmn crucisj dis- 

 proving the reality of tlie Newtonian fits. 



After this result of the experiment, am\ the admission 

 of the retrospectors as above quoted, it niiirh.t have been 

 expected that they would no longer have resisted such evi- 

 dence, or the just conclusion from it : — but no such thing ;f' 

 we now find them disputing the point as much as ever, by 

 7tetv assertions and contradictions, as totally groundless as 

 that whose fallacy we have convicted them of. They imme»* 

 diately after the aijove quotation, now allege, that on ac- ■ 

 count of corpuscular repulsions, &c., the wedge of air de- 

 scribed by Dr. IJerschcl could not have been so thin as 

 his measures, which before they did not challenge, show 

 it to be; or so thin as to jiroduce streaks accordinq^ to the 

 Newtonian doctrine of the fits ; than which nothing can 

 be more wide of the fact. ; .. , 



But, in another place, \te find something prodigiously 

 inconsistent with all this contention for extreme thinness 

 of the wedge, before it is capable of showing streaks. In 

 page 410, where the retrospectors want to set aside Dr. 

 Herschel's explanation of the bow streaks which he has 

 shown to be occasioned by the application of a plain re- 

 flecting surface under the base of the prism, how do they 

 do so? Still i)y resorting to the Newtonian doctrine o?' 

 the fits. An(\ now'theywould have these bow-streaks tai 

 be produced by the plate of air between thebase of ihfe' 

 prism and the reflecting surface applied to it, in conse- 

 quence, they say, of i\\*t great thickness of this very plate, 

 occasioned by their corpuscular repulsions. We shall say 

 no more of such flagrant contradictions. In the sanjc 

 spirit, in the concluding paragraph, page 412, they deny 

 that wfiat Dr. Herscliel calls th^ critical separation is ca- 

 pable of producing the bows; not perceiving that sir Isaac 

 Newton has explained the formation of his blue bow on 

 this verv principle, as Dr. Hersthei has explained his red 

 bow. ' ' ' ^ ' 'i 



In short, both attacks of the retrospectors abound with- 

 siTTiilar inconsistences and conti;adictions, which we think' 

 w^holly undeserving of notice ;• as' with such'tippoitents we 

 cotisider fiirther drscussi'ons tcf-bc^Vairi. 



'XLIX. On 



