On anew systematic Arrangement of Colours. 327 
cording to my ideas of its analogy to the other bodies 
which contain chlorine; but I am not desirous, in the pre- 
seni imperfect and fluctuating state of chemical nomencla- 
ture, to press the adoption of any new word, particularly as 
applied to a substance not discovered by myself. 
I am, my dear sir, very sincerely yours, 
Humeury Davy. 
LIV. Ona new systematic Arrangement of Colours. By 
T. Forster, Esq. 
To Mr. Tilloch. 
S1r,— Since my communication on the subject of a more 
perfect nomenclature and classification of colours, I have 
met with Mr. Sowerby’s work on Colours, and have had 
some conversation with the author on this subject. He 
expressed his opinion to me that such a nomenclature might 
be formed as I have hinted at in my paper; namely, one 
which should express their varieties by reference to the pro- 
portions of the primitive colours which made up each of 
the compounds. 
According to the most recent theory, there are only 
three primitive colouys, each of which is distinct from the 
other two, and none of which can be artificially made by 
any compound of other colours; they are, for example, 
the red, the blue, and the yellow of the prism. The pri- 
mitive red should be distinguished from all other reds, as 
the latter are mixtures of the former, with some proportions 
of one or other of the remaining colours. The same ob- 
servation holds good with respect to the primitive yellow 
and blue. In the formation of different colours, the pri- 
mitive colours are mixed either in binary or ternary com- 
pounds. 
The binary compounds are: Firstly, the combinations of 
red and yellow, which, according to the proportion in which 
they are combined, make all those varieties between red 
and yellow, which, when mixed in pretty equal quantities, 
are called orange colour. Secondly, the combinations of 
red and blue, which make all the crimsons, lake colours and 
purples. And lastly, the combinations of yellow and blue, 
making all the varieties of green. 
The ternary compounds are the browns, various, indeed, 
according to difference of the proportions. Accordingly as 
one or theother preponderates, it will bea blueish, a reddish, or 
X 4 a yellowish 
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