MONTHLY MAGAZINE. 
No. xitvin.] © AUGUST 1, 1799. [No. I. of Vor. VIITs 


On the 20th day of Fuly was publifbed, theSurPLEMENTARY NUMBER fo the Seventh Volume 
, of the => ae Ue MAGAZINE, containing—-A comprehenfive Retrofpect of the Progrefs of 
Britisu Literature during the laf fix Months—-and fimilar Retrofpects of GERMAN g 
Frencu, and SPANISH LITERATURE} 
with INDEXES, TiT1e,y &c. 


ORIGINAL COMMUNICATIONS. 
For the Monthly Magazine. 
EXPERIMENTS ON COLOURS. 
fe i a ray of light pafs through a elafs 
prifm, it forms a fpeétrum; which, 
Sir {aac Newton conceives, may be com- 
pofed of the following feven colours ; viz. 
aft, violet; ad, indigo; 3d, blue; 4th, 
green; 5th, yellow; 6th, orange; 7th, 
red, 
equal parts, each of thefe colours (actord- 
ing to Sir Ifaac Newton) will occupy that 
proportion of parts which is affigned to 
it in the circular {pectrum. See Fig. 1. 
And if thefe colours be mixed, by making 
the circle revolve fwiftly round its centre, 
they compofe white. 
It is generally known that indigo and 
ited, when mixed in proper proportions, 
produce violet; that blue, and yellow, 
"produce green; and that yellow, and red, 
yproduce orange. 
Does it not then feem probable, fince 
andigo, blue, yellow, and red, are capable 
. #f producing the other three colours, viz. 
wiolet, green, and orange, that indigo, blue, 
#ellow, and red, may be the only original, 
-or elementary colours, at leaft that, if 
wmixed tn due proportions, they should pro- 
duce the effedt of the feven, or compofe 
rwhite. 
(‘EXPERIMENT 1. SceTable, Fig.2, A.2, 
To afcertain upon this fuppofition the 
yeroportion. of indigo,’ blue, yellow, and 
sved, in white. 
See the {peftrum for the following pro- 
"portions, viz. 

‘Indigo 40 2 5 ee £053 
sBluc 64 32° 35 S385 
Rellowg8 °°. “ee £2524 
Nae wes Bkees 
pair Tiidigo 
bAs 193 360 40 74 11% Indigo 
Blue 
193 360 So 111477 Blue 
Yellow "> 
(e] 2) * 
194% 360 Rae 89 353 Yellow 
18 
193 350 45 83482 Red. 
360 
| Montury Mae. No, xryu, 
If this fpeétrum be divided into 360. 
A circle then painted 74 ie indigo, 
111 477 blue, 89 423 yellow, 83 ioe 
red, fhould produce white. 
(In future I foall not fiate the procefs for 
difcovering the proper proportions of the dif- 
Serent colours, but merely flate the refults, 
Sor the fake of brevity, and; for the fame 
reafon, I fhall occafionally ufe the initial let- 
ters of the colours enly. | 
But it is contended, that although 4 
violet may be produced, by blending red, 
and indigo; a green, by blending blue, 
and yellow ; and an orange, by bleriding 
yellow, and red: yettheviolet, green, and 
orange fo produced, are fadctitious and com=_ 
bined, and not like the violet, orange, and 
green, prifmatic colours, becaule if thefe 
colours, fo compofed, be paffed through a 
fecond prifm, they will be feparated into 
the two elementary colours compofing 
them; which, it is faid; cannot be done 
with the prifmatic violet, green, and 
orange. Now Experiment A s, and the 
confideration, that-the faétitious violet, 
green, and orange, are each compofed of 
the colours immediately contiguous to 
them, the one to the right hand, and the 
other to the left hand, in the priimatie 
{pectrum ; as well as the objection mén- 
tioned before, (which, if it be conelufive, 
proves ail the feven colours of the prifn ta” 
be equally elements), thefe citcumftances 
concur in fuggeftiig a fuppofition; that 
any factitious prifmatic colour’, may be pro- 
duced by the twa immediately contiguous. 
EXPERIMENT If. 
Upon this {uppofition a'circle painted, 
45 or 190 5° Red 

40 169 35 Indigo 
Should compofe 360 —- Violet. 
See Table B te | 
EXPERIMENT III. 
Bo or 205 2°22 Violet 
i40 
6c 154 40. Blue 
Should compote 360 Indigo. 
See Table B 2. . 
3 EXPERI- 
