^difcellanea Cwiofa. I o I 



greffive Motion being communicated to it by 

 that ftroak, its part^oa that fide, where the Mo- 

 tions confpire, muft prefs and bear the contigu- 

 ous Air more violently than on the other, and 

 there excite a Relu£tancy and Reaction of the Air 

 proportionably greater. And for the fame Rea- 

 lon, if the Rays of Light fhould poliibly be glo-" 

 bular Bodies, and by their oblique PafTage out of 

 one Medium into another, acquire a circulating 

 Motion, they ought to feel the greater refi fiance 

 from the ambient iEther, on that fide, where 

 this Motion confpires, and thence be continually 

 bowed to the other. But notwithstanding this 

 plaufible ground of fufpicion, when I came to 

 examine it, I could obferve no fuch Curvity in 

 them. And befides ( which was enough fur my 

 purpofe) I obfcrv'd, that the difference 'twixt the 

 length of the Image, and Diameter of the Hole, 

 through which the Light was tranfmitted, was 

 proportionable to their diftance. 



The gradual removal of thefe fufpicions, at 

 length led me to the Exper-imentum Cruris, which 

 was this; I took two Boards, and plac'd one 

 of them clofe behind the Prifm at the Win- 

 dow, fo that the light might pafs through a 

 fmall hole, made in it for the purpofe, and fall 

 on the other Board, which I plac'd at about 

 twelve Feet diftance, having fir ft made a fmall 

 hole in it alfo, for fome of that incident Light to 

 pafs through. Then I plac'd another Prifm be- 

 hind this fecond Board, fb that the Light, tra-, 

 je&ed thrpugh both the Boards, might pafs thro 

 that alfb, and be again refracted before it ar- 

 rived at the Wall. This done, I took the firft 

 Prifm in my Hand, and turn'd it ro a ad fro flowly 

 about its Axis, fb much as to make the feveral 

 parts of the Image, caft on the fecond Board, 

 H 3 (ucceilively 



