360 Dr Newbigging on certain Circumstances affecting 



vation of the ornament, and the colours ai*e not so deep or 

 brilliant. ? 



In the progress of niimerous investigations, I found that 

 there was invariably an accurate representation of the orna- 

 ment, provided the colour was of bright green, and slightjy 

 elevated as it is when affixed to the china by the former ope- 

 ration, but could observe no effect whatever in those cases 

 where the decorations appeai-ed to have been produced by the 

 latter process. With the view of further illustrating the sub- 

 ject, I caused the seven prismatic colours to be painted on 

 separate lozenges at the bottom of a cup, and had them coated 

 with copal varnish. Out of four experiments which I made 

 with this cup, I procured no change excepting in one instance, 

 and that was merely a light mottling, barely appreciable, but 

 in no respect corresponding with the effect produced by the 

 green ornament in my former experiment. Up to this period, 

 there appeared to me to exist two conditions, either of which 

 might effect the result, namely, the brightness of the green 

 ornament, and its partial elevation on the surface of the china ; 

 — the first being apparently connected with some chemical 

 cause ; and the latter possibly with the pressure upon the clot, 

 or the order of distribution of the globules of which it is com- 

 posed, as affected by the elevation of the ornament. 



Oxygen being the recognised agent, producing the change 

 from the dark purple of the venous, to the bright vermilion tint 

 of the arterial blood, in the absence of any other probable ex- 

 planation, it suggested itself to my mind that, possibly, there 

 might be some peculiar affinity betwixt the bright green and 

 that element of the atmospheric air, causing some of it to linger 

 on the surface of the ornament, when the rest of the air had 

 been expelled from the cup by the entrance of the blood. I 

 resolved therefore to try whether another substance, similarly 

 affected by oxygen, would produce any thing like a similar re- 

 sult. For this purpose I made a solution of isinglass with pro- 

 toxide of iron, the effect of oxygen on which is to convert its 

 leaden colour into that of a reddish brick, and poured it liquid 

 into a cup, Avith a bright green device, that had, in every in- 

 stance in which it had been employed, struck the correspond- 

 ing vermilion image on the blood. On inverting the coagiilum 



