tfe. . Y» V.i 
ON 
COLOURS, 
THEIR ARRANGEMENT IN GROUPS. 
It is not intended in the following pages to explain the nature, or cause 
of colours, or to speak of the theory any further than as it relates to the 
effect of colours in painting. To that end it is necessary to observe, that 
the rays of the sun convey colour as well as light and heat; that there are 
said to be seven original, or primary colours, which are all visible in the 
rainbow, or through a prism; red, orange, yellow, green, blue, indigo, 
violet. Notwithstanding this, some are of opinion, that there are in reality 
only three original colours, red, yellow, and blue ; others think it probable 
that there are four, including indigo, differing in opinion from philosophical 
experiments on the rays of light. Be this as it may, it is certain, that by 
compounding the first three colours the other four are produced, at least 
they are very nearly imitated : for instance, if you mix red and yellow, they 
produce orange; if yellow and blue, you get a green ; with red and blue, 
a violet; and with blue and violet, indigo ; thus are four of the colours 
produced by the other three. 
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