1815.) Proceed'uigs of Philosophical Societies. 30* 



Article XI. 



Proceedings of Philosophical Societies. 



ROYAL SOClEXy. 



Fel. 23. — At this meeting a part of a paper by Sir H. Davy, 

 entitled, Some Experiments and Observations on the Colours used 

 in Painting by the Ancients, was read. 



March 2. — At this meeting the conclusion of Sir H. Davy's 

 paper was read. The following are the results of his observations : — 



The experiments were made on colours found in the baths of 

 Titus, in the baths of Livia, and other ruins of Ancient Rome, as 

 well as of Pompeii. Some of them were discovered in vases found 

 below the ruins of the Palace of Titus. These were identified with 

 the colours employed in various fresco paintings in this palace. 



Three kinds of red were found in a vase two years ago ; the first, 

 approaching to orange, was minium ; the second, a dull red ; and 

 the third, a purplish red, were ochres. Another red, found in 

 fresco paintings, was plainly' vermilion, called minium by the 

 Romans, who gave the name of cerussa usta to our minium, which 

 Sir H. Davy supposes to have been a natural carbonate of lead burnt. 

 The yellows are ochres diluted with different quantities of chalk, 

 and yellow oxide of lead, or massicot. No sulpiiurets of arsenic 

 were detected, though they were known to Pliny and Vitruvius. 



Lumps of a deep blue frit were collected among the baths of 

 Titus, which were composed of soda, silica, and oxide of copper. 

 AH the blues were composed of this compound, and the intensity 

 of their colour was reduced with carbonate of lime. Sir Humphry 

 supposes this to be the blue colour described by Theophrastus as 

 having been discovered bv an Egyptian King, and as manufactured 

 at Alexandria. The ccerulium of Vitruvius was made by heating 

 sand, natron, and copper. 



No traces of indigo have been detected, though it was known to 

 the ancients. Cobalt was observed colouring glass. 



The greens are carbonate of copper, except one which approaches 

 to olive. 'J'his is the common green earth of Verona. Sir H. 

 thinks it not improbable that many of the carbonates of copper 

 were orii;inally acetites. 



In the bottom of a broken vase found in the baths of Titus a 

 substince externally cream-coloured, internally carmine, existed, 

 whicli was combustible, and left about -^-^ of siliceous, aluminous, 

 and calcareous earths. It is regarded as a like, though it is im- 

 possible to determine whether it be animal or vegetable. 



The browns are mere oxides of iron, and sometimes mixtures of 

 iron and manganese. 



No cerusse was found among the whites, which were generally 

 carbonates of lime and fine white clavs. 



V 2 



