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mal a strong Conjecture in favour of his New Doctrine; I having formerlyobservcd the like Chain of Infercnces upon search into Natural Tvuths. Butnuce leveral Experiments of Refractions remain stili imtouchcd by him,i conceivcd a further search into them would be very proper, in orderte afurther dilcovery ot the Truth ot his Aflertion. For, accordingly as tliey aref.mnd cithcr agrecing with, or disigreeing front, his New Theory, they tnustneeds much strengthen, or wholly overthrow the sinte. . The Experiments Ipitchcd upon for this purpole are as follow.

i. Having frequcndy obferved, that the Form of Objects viewed in theJVlicrofcope (or rather of the Microlcope it se 10 conlists almost in an indivi-lible Point, I concluded, two very Irrtall pieces of Silk, the one Scarlet theother Violet Colour, placed near together, fhould, according to Mr. NewtonsTheory, appear in the Microlcope in a very disterent drgrce of Clarity, inrcgard their Unequal Refrangibility must causc the Scarlet Rays, or Species, toover-reach the Retina, while placed in the due Focus of the Violet ones,and consequently must occasion a sensible Confusior, in the Vision of the for-mer, one and the sime Point ol the Scarlet Object aftccting leveral Nerves inthe Retina. Yet upon frequent Tryals I havc not been able to perceivc anyInequality in thispoinr.

a. The Second Experimenti made in Water. I took a Braß Ruler, andfastning thereunto leveral pieces of Silk, Red, Yellow, Green, Blue, andViolet, I placed it at the Bottom of a Square Veste! of X Vater : then I reti-rcd fr«m the Vestel so far as not to be able to lee the aforesiid Ruler and Co-loured Silks, otherwise than by the Help of the Refracted Ray. Now, didMr. Newtons Doctrine hold, I conceived I fhould not lee ali the ntentionedColours in a Streight Line with the Ruler, in rcgard the Unequal Refrangi-bility of Disterent Rays must needs dilpl.tce Ionie more than others. Yet inEftect, upon many Tryals, I constantly found them in as Streight a Line, asthe bare Ruler had appeared in.

z. To advance this Experiment, I adjoined a Second Refraction to theformer of Water, by placing my Prilm Io as to receive pcrpendicularly theRefracted Species of the Silk and Ruler; whereby only the Emergent Speciessuftercd a second Refraction. But stili with equal Succels, as to their appear-ing in a Streight Line to the Eye placed behind the Prilm.

4 . To these two Refractions I further added a third, by receiving theCo-loured Species obliquely upon the Prilm; whereby both Incident and Emer-gent Species lustered their relpective Refractions. But stili with the lameSuccels as formerly, as to the Streight Line they appeared in.

For further astu rance in this Experiment, lest preposieilion, occasiondfrom previous Knowledge of the Silks situation in a Streight Line, mightpolTibly prejudice the Judgment of the Eye (as lometimes 1 ha ve observed tohappen to the Judgment the Eye pasteth upon the distance of Objects) I called»ntothe Room lome unconcerned Perlons, wholly Ignorant of what the Experi-ment aimedat; and demanding whether they siw not the Coloured Silks andRuler in a Crooked Line ? They Anlwered in the Negative.

5 . The

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