33 
I had lately given to me small portions of several colours on 
walls from Pompeii. These with some similar portions obtained 
from a Eoman Yilla, at Collingham, excavated some years ago, 
have been made the subject of experiment. 
The colours were—yellows, greens, reds, and a rose colour. 
The yellows were three in number, and I found No. 1 to be 
a yellov/ ferruginous earth with clay. No. 2 was Limonite, 
mixed with gypsum. No. 3 was a yellow mixed with chalk. 
It is in the first place proper to mention that the word Ochre 
is applied in mineralogy to any product of decomposed ores, as 
Cobalt ore, &c., but in ordinary and popular language, and with¬ 
out definite accuracy, it is applied to any combination or mixture 
of the earths with iron which can be used for pigments and the 
like. Hence, as the colour is light or dark, we have yellow, 
red, and brown ochres. They are produced by the disintegra¬ 
tion of iron ores, and notably of the Hematite forming the red, 
and of Limonite, or the hydrated oxide of iron, giving rise to the 
formation of the lighter ochres, the tint being moreover varied 
by admixture in different quantities with light coloured earths. 
The admixture of them, I found, with clay, chalk or gyp¬ 
sum, admits of a probable explanation, by reference to Pliny 
who tells us that certain colours were mixed with other sub¬ 
stances to render them lighter, and thus obtain various tints, 
whilst other colours required an under coating, or some prepara¬ 
tion of the surface for their reception. This latter statement 
may account for the presence of gypsum in No. 2, assuming 
that it did not happen to be an ingredient of that particular ore 
from whence the colour was obtained. 
Pliny describes numerous colours under different names, all 
of which appear to be those which we should now call ochres. 
‘‘ Sinopis, the author writes, was discovered in Pontus, and 
hence its name from the city of Sinope. It is produced also 
in Egypt, and the Balearic isles, but the be^t is found in 
Lemnos and Cappadocia, being extracted from quarries there. 
In the native mass it has its own proper colour within, but is 
spotted on the exterior, the antients made use of it for tone.’’ 
Pliny here uses in the original the word splendor ” supposed 
by ’W’ornum to be the equivalent of our word tone, which 
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