220 
the sun’s rays thereon which injure and destroy the 
colours in work of this nature. The laboratories which 
were formerly carried on at the mines in Ephesus are now 
transferred to Rome, on account of mines of the same sort 
having been discovered in some parts of Spain, whence 
the clods are brought and worked by manufacturers at 
Rome. These laboratories are situated between the tem- 
ples of Flora and Quirinus. Vermilion is occasionally 
adulterated with lime. The following is a method by 
which its goodness may be proved. Let the vermilion 
be placed on an iron plate over the fire, and remain 
till the plate is red hot: when the heat has changed the 
colour, and it appears black, let the plate be removed 
from the fire. If, when cooled, it returns to its original 
colour, it may be considered pure. But if it remain of 
a black colour, it is quite clear that it has been adul¬ 
terated. I have written all that I remember respecting 
vermilion. Chrysocolla comes from Macedonia, and is 
found in the vicinity of copper mines. Minium and 
indigo, by their names, indicate the places from whence 
they are obtained.