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mcnt: Fori have try'd it often ; fometimes toobfcrve thecircutn- 
ftanccsof it, fometimes in order tofurther Experiinents,and fome- 
tinies to fliow it to others, and in all my tryals the fuccefs was the 
fame* But whereas Mr, Line thinks,! tryed it in a cloudy day,and 
placed the Prifm atagreacdiftancefrom the hole of the window ; 
the Experiment will not fucceed well if the day be not clear , and 
the Prifm placed clofeto the hole, or fo near at leaft, that all the 
Sun's light that comes from the hole may pafs through the Trifm 
alfo, fo as to appear in a round form if intercepted by a paper im- 
mediately after it has pad the Prifm. 
When Mr. Line has tryed this, I could wifli,he would proceed 
a little further to try that which I call'd the Exferimentum Cruets^ 
fteingCif Imif-remembernot)hedenies thatas well as the other. 
For when he has tryed them (which by his denying them , I know 
he has not done yet as they fhould be tryed)I prefume he will reft 
fatisfied. 
Three or four days after you gave mc a fight of Mr.L/»tf's fecond 
Letter, I remember 1 thereupon fliow'd the firft of thefe two Expe- 
riments to thatGentleman whom you found with me,when yougave 
me that vifitjand whilft 1 was (hewing it to him, A//, (a member of 
the R.Smety) came in and I (hewed it to him alfo. And you may re- 
n)cmbcr,that R, H. two or three years agbe in a Letter read before 
iheR. Society, and tranfmitted to me,gave teftimony not only to the 
Experiments queftioned by Mr.L/W,buc to all thofefet down in 
my firft Letter about Colours, ashaving rryed them hinvfelf; and 
when you read Mr. Line's Letter at a meeting of thefaid Societjr^ 
and was pleafed to do me the favour to propound the Experi- 
ment to be tryed in their prefence fpake of it to them as 
a thing not to be queftioned. But if it have not yet be^n tryed be- 
fore them, and any of them, upon Mr. Line's confidence,doubt of 
if, I proraife when I fliall have the happinefs to be at any more of 
their AflTemblies, upon the leafl: hint, to fliew 'em the tr3'al of it ; 
and I hope, I ftall not be troublerome, becaufe it may be tryed 
(though not foperfefliy)cven without darlaiingr-a room, or the 
ex pence ofany more tim^tha:n half a quarter of an hour ; although, 
if Mr, Line perfift iii his denya! of it , I could wifii it mighi:. be 
tryed fooner there , than I fliall hayean opportunity to be among 
