( 6 10 ) 
and Blue will be equally raifed as at T. This muft have 
been Signior Rizzetti ' s Miltake, when (in Tage^.) 
he fays that one Colour was raifed higher than the 
other by two Line?, at ten Foot Dilhnce, but not at 
all at five Foot j for feveral of the Perfons prefen t at 
my Experiments, made the fame Miftake at firft before 
they could perform the Experiment in manner above- 
mentioned ; which they atlaft did, and found the Co- 
lours feparated moft atthegreateft,and lead at the ieaft 
Diftance, This miltaking a Refiedion for a Refradion, 
has been the Occafion of feveral more Error?, and Dif- 
ficulties to be met with in Signior Rizzetti *s Book. 
F. XPERIMENT III. F I G. VI- ' 
A Candle K, refleded from the Surface A B of the 
Prifm A B C, appeared very faintly to the Eyeat E, as 
a weak Image at k ; becaufe the Rays incident at I, pafs 
moft of them through the Prifm, and go on to R, fe- 
parating from one another according to their different 
'Degrees of Refrangibility } whiift a few of them are 
refleded to the Eye in the Diredion I E. 
'But if the Prifm be in the Pofition ACB ( Fig.y .) 
moft of the Rays of the Candle K, incident at 1, on the 
Plane A B (after having paffed perpendicularly through 
the Plane BC) are refleded, and palling perpendicularly 
through AC, go into the Eye -at E 5 which fees a very 
ftrong Image of the Candle art k, whiift very few Rays 
go down to R to produce Colours. 
This Ihews that the Rays of Light pafs with more 
Facility through Glafs (a-denfe) than through the 
Air (a rare) Medium } contrary to Rizzetti ’s Af- 
fertion. ..... r'f •' 
,, tr, 1 A 
L. L. i' 
E X. 
