( >? 6 )

Considering that the Rays coming from thc Planet Venus, are much lefsinclined one toanother, than thole, which conie from the oppolite parts ofthe Sun's dilque; 1 oncctryed an Experiment or two with her Light. Andto malte it fuffncicntly ffrong, Ifound itneceslary tocollect it Erst hy a broadLcns, and then interposing a Prilin between the Lens andits Focus, at suchdiffance, that all the Light might paß through thc Priim , I sound thc Fo-cus, which betöre uppeared like a Lucid point, to be -dravvn out -into a Longsplendid Line by the Prifms Refraction.

Concerning the fccon.l Experiment, I have occasionaüy oblcrvcd, that bycovering both ends of the Priim with Paper at leveral diffances from the mid-dle, the Breadthof the Solar Image will be increakd or diministied as much,as is thc Aperture of the Priim, without any Variation of the Ler.gth: Or,if the Aperture Ire augmented on ali sides, the Image on all sides, will beso much and no ruo.rc augmented.

Of the Thinl Experiment 1 have occasion to ipc.ik in my anlwer toan >ttufPerlon; where you will sind the Effects of two Prifms,-in all crols poiitionsof one to another, delcribed. But if one Prifin aione be turned about, t'heColourcd Image will only be tranffated from place to place, delcribing a Cir-cle, or lome other Conick Scction on thc Wall, on which it is projected,without luftering any alteration in its Ihape, unlefs fuch as may ariie from theobliquity of the Wall, or casiial change of the Prilnis obliquity to thc Sun'sRays.

The eftect of the Fourtb Experiment I have already insinuated, tclilng vonthat Light palsing through parts of the Priim of divers thicknesies, did lli.lexhibit the lame Phxnomena.

TbeGenuint ’III. I cannot think!t effectual for determining truth, to examinethelever.ilMethodos exn- ways by which Phxnomena may he cxplained, unleß where therecan be a per-,h ^J he ~ Enumeration of all thole ways. You know, the proper Method for in-Newton, n. 85. quiring aster the Properties of things, is to deduce them from Experiments,f. 5004. And 1 told you, that the Theory which I propoundcd, was evinced tome, notby inferring ’eis thus beenufe not othcmijc, tiiat is, not by deducing it onlyfrom a confutation of contrary liipposirions, but by deriving it from Experi-ments concluding positively and directly. The way therefore to examine itis, by considering, whether the Experiments which I propound do prove tholeparts of the Theory, to which they are applyed ; or by prosecuting otherExperiments which the Theory may fuggest for its examination. And this1 would have done in a due Method; the Laws of Refraction being through-ly inquired into and determined, before the Nature of Colours be taken intoconsideration. It may not be amifs to proceed according to the Series ofrhese Queries; which I could wi(h were determined by the event of properExperiments; declared by thole that may have the Curiosity to examinethem.

1. Wlietber^j, that are alike Incident on the sinne Medium, have ZJne-ejual {{efrattions ; and how great are the Incqunlities of their Refractions at a-ny Incidence ?

1. Whut