no Sir Humphry Davy’s experiments and observations 
bright blue tint produced by oxide of copper. There are 
several different shades of green employed in the baths of 
Titus, and on the fragments found near the monument of 
Caius Cestius : in the vase of mixed colours I found three 
different varieties ; one, which approached to olive, was the 
common green earth of Verona ; another, which was pale 
grass green, had the character of carbonate of copper mixed 
with chalk ; and a third, which was sea green, was a green 
combination of copper mixed with the blue copper frit. 
All the greens that I examined on the walls of the baths 
of Titus were combinations of copper. From the extreme 
brilliancy of a green which I found in the vineyard to which 
I have so often referred, I suspected that it might contain 
arsenious acid, and be analogous to Scheele’s green ; but on 
submitting it to experiments, it afforded no indications of this 
substance, and proved to be a pure carbonate of copper. 
The greens of copper were well known to the Greeks ; the 
most esteemed is described by Theophrastus and Diosco- 
rides under the name of x^xroncXha,, and is stated by both to 
be found in metallic veins. 
Vitruvius mentions chrysocolla as a native substance found 
in copper mines, and Pliny speaks of an artificial chrysocolla 
made from the clay found in the neighbourhood of metallic 
veins, which clay was most probably impregnated with cop- 
per. He describes it as rendered green by the herb luteum. 
There is every reason to believe, that the native chrysocolla 
was carbonate of copper, and that the artificial was clay 
impregnated with sulphate of copper rendered green by a 
yellow die. v 
Some commentators have supposed that chrysocolla is the 
