( 44-6 ) 
To lhew that the Colours in this SpeBrum were Am- 
ple and homogeneal Lights, I made the following Experi- 
ments. 
EXPERIMENT IX. 
Having made an Hole h in the Paper which receiv’d 
the colour’d SpeBrum, I fuffer’d the red Light to pa(s ; 
which being refraded by a fecond Prifm, fell upon ano- 
ther Paper at T , where it appear’d Rill Red whether feen 
with the naked Eye or Prifms of different refratRing An- 
gles. To the Eye which faw it thro’ the Prilm V, it ap- 
pear’d indeed lower as at t, but red, round and unchang’d. 
I made the Experiment upon all the Colours, which by 
this means appear’d to be Ample and homogeneal. See Fig. 
n. Where the fame Letters denote the Lens, Prilm and 
firft Paper. 
Thro’ the fame Lens and Prifm the SpeBrum was made 
to fall on a Book ; then thro’ the Prifm Fit appear’d un- 
chang’d ; and the Letters in the Book which crofs’d the 
SpeBrum , were as di(tind as when feen with the naked 
Eye. See Fig. 23. 
N. B. The Axis of the Prifm F ought to be perpendi- 
cular to the long Axis of the SpeBrum s m thrown on the 
Book, which will appear as at a /*. ; and the Prifm in the Po- 
rtion reprefented at FjWith its flat Side towards the Nofe: 
for that is the moft convenient Pofition for looking at the 
SpeBrum in thefe Experiments. 
I fuffer d the purple Ray only to pafs thro’ the Hole h 
and fall upon a Book at P , the Letters of which appear’d 
at 7 t, and were as diftind thro’ the Prifm ^as when feen 
with the naked Eye : and I had the fame Succefs with all 
the other Rays. See Fig 2,4. 
But if a Sun-Beam as r conies thro’ the Hole /i/d iredly 
upon the Book at W> an Eye looking at it thro’ a Prifm 
at 
