of the Tessera in a Roman Pavement. 51 



this red tint to glass by a very ingenious method, and it was the 

 substance used for this purpose, namely copper, which covered 

 over the tesserae as the surface of the glass had become decom- 

 posed in the form of a carbonate of that metal. 



This fact is curious in its bearing upon the pavement as a work 

 of art ; as so harmoniously are the colours arranged in all the 

 figures that it may almost be taken for granted that, as in this 

 instance, when there is an exception in this particular, it is due 

 to some subsequent change having taken place in one or other 

 of the colours. In the case before us our first tracing was co- 

 loured with the verdigris-green : it was unsatisfactory ; but on 

 making a new tracing and colouring it according to our amended 

 observations, it at once became harmonious in colour, and as- 

 sumed an intelligible form, though all our colouring will not 

 enable us to convey the idea of ruby-gemmed flowers like the 

 substance used, the transparency of glass contributing much to 

 the general effect. 



