* At Liege,

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n. ne» p. 2IA.

A Refft by Mr.Fr. Linus.

&, 121 ./. 4 - 9 ?»

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thro’ the fame little Hole. And this \ve behold also in the true Sun-beams,when they enlighten the whole Prisin: for altho’ in a Clear Heaven, the Raysof the Sun paliing thro’ the fuid Hole, never malte a Spectrum Longer thanBroad, because they then occupy but a final 1 part of the Prisin; yet if theHole be so much bigger as to enlighten the whole Prisin, you {hall present-ly sce the Length of the Spectrum much excced its Brendth; which excesswill be always so much the greater, as die Length of the Prisin excccds itsBrcadth. From whence 1 conclude, That the Spectrum, this Lcarncd AuthorJaw much Longer than Broad, was not astected by the true Sun-beams, butby Rays proceeding from löme bright Cloud, as is l'aid ; and by Consequcnce,that the Thcory of Light groundcd upon that Experiment cannot subsist.

What I have here faid, needs no other Conhrmation than meer Expcrience,which any one may quickly try ; neither have I only trycd the sime upon thisoccasion,but neur 30 Years ago (hcwed the sitme, together with divers otherExperiments of Light, to that Worthy Promoter of Experimental Philosophy,,Sir Keuchn Digby, who Corning into thesc Parts to take the Spaw Waters, re-sorted often-times to my Darkned Chamber *, to lee thefe various Phaenomenaof Light, made by divers Refractions and Reflcctions, and took Notes uponthem; which Indtistry if they also bad uftd, who endeavour to Explicatethe aforelaid Disterence between the Length and Breadth of this ColourcdSpechum, by the reeeived Laws of Refraction, would never have taken so im-posttbly a Task in band.

1 . Theso Animadvcrfions seem to need no other Ansivcr but this, that youwould be pleasid to confidcr the Scheme in Mr. Newtons sccond Answer toP. Pardies, and rest aflured, That the Experiment, as ’tis represented, wastry’d in Clear days, and the Prisin placed closo to the Hole in the \\ indow>so that the Light had no Room to Diverge, and the Colourcd Image madenot Parallel (as in that conjecture) but Transverse to the Axis of the Prisin.

3. If thefe AJscrtions be admittcd , they do indeed dircctly cut ofi what Ifaid of Mr. Newtons being deceivcd by a bright Cloud. But if we comparethem with Mr. Newtons irrst Relation of the Experiment, it will evidently ap-pcar, they cannot be admitted, as being dircctly contrary to what is there doliyered. For there he teils us, Ehe Ends of the Colourcd Image, i:e saw cn theoppefite Wall, near five times as Long as Broad, feemed to be Semicircular. Nowthefe. Semicircular Ends are never seen in a clear day, as Expcrience shews.From whence follows against the first Affertion, that the Experiment was notmade in a clear day. Neither are thoß Semicircular Ends ever seen when thePrisin is placed dose to the Hole; which contradicts the sccond Assortiern.Neither are they ever ßen when the Image is Transverse ta the Length or Axisof the Prisin, which dircctly opposes the third Aflertion. But if in any ofthefe three Cafes, the Image be made so much Longer than Broad (as eafilyit may, by turning the Prisin a little about ks Axis, near five times as Long asBroad) then the one End thereof will run out into a Iharp Cone or Pyramislike the Flame of a Car.dle, and the other into a Cone somcwhat morebjunt; both which are far from ßeming Semicircular: Whereas, if theImage be made not in a clear day but with a bright Cloud, and the Prisin not