19 Upon the variegated Colours of Bodies 



by a small ribbon cut precisely in the midst of a circle 

 formed of a series of concentric coloured rings. The nature 

 of the phasnomenon, therefore, was here manifested very 

 distinctly; for the exterior ring was nearly three centimetres 

 in diameter, and the others decreased interiorly, with inter- 

 vals of some millimetres. Nothing was wanting to com- 

 plete the figures but to operate upon a large plaie of steel, 

 suspended horizontally above the point of the flame ; in this 

 case, I should certainly have obtained entire circles af rings. 



1 did not happen to have such a large plate of steel at 

 hand, but I made use of a sheet of tinned iron, which, with 

 appearances analogous to the preceding, gave very brilliant 

 colours, on account of the natural white of the substance. 

 When looked at in a proper direction the colours appear still 

 TROXt lively, viz. chiefly yellow, red and blue, which form 

 together a spot in which the blue occupies the centre, sur- 

 launded with red, and beyond that again yellow, with in- 

 termediate gradations of shades. 



Nothing in the faculty possessed by tin of oxidating and 

 farming salts, indicates any thing like colours corresponding 

 ta the above ; in addition to this, the periodical streaks upon 

 the steel watch-spring evidently belong to a series of rings; 

 we must therefore conclude that this phaenoraenon belongs 

 simply to the class of coloured rings. 



Another experiment made upon a gold ring also produced 

 repeated traces of rings ; and in this case, the idea of oxida- 

 tioai is almost out of the question. 



A eopfjer wire gave me similar appearances, although 

 more feebly ; but I have remarked them very distinctly upon 

 this same metal when made into the flues of stoves. Lead, 

 when we melt it, also exhibits these sorts of colours when 

 cooled, even upon its inferior surface, not exposed to the 

 contact of the air. 



With respect to the action exercised by caloric upoo the 

 metal in these various examples, I shall not assert that it 

 has altered the size of the particles; for how can we con- 

 ceive that a substance can, without becoming of another 

 nature, vary in the disposition of the constituent elements 

 of its molecules J But I can more easily comprehend that 



there 



