Obfervations on Lead Ore. 883 
further variation. All the colours are very vivid, and 
each feems to go through all the fhades belonging to it 
before it is changed into the next in order. 
The formation of thefe colours may be explained 
from what has been advanced by Sir Isaac newton, 
and illuftrated by the very ingenious experiments of Mr. 
delaval, relative to the lize of the particles conftituting 
coloured bodies. 
5 R 2 
