Chemical Science. 365 



concentric rings, which constantly possessed the same order. 

 The external ring was darkish yellow, to which succeeded a 

 deep red beneath a purple ; and the third was a deep azure, 

 which passed into a clear sky-blue ; then returned the yellow, 

 followed by the purple and the azure, and so on. These rings 

 may be seen by the naked eye, but are best viewed by a lens. 

 The number of series is not constant, being three or four, up to 

 seven. They are always round a dark pulverulent central spot, 

 which is an oxide of silver. All attempts to produce these rings 

 on platinum failed. 



Sig. Fusinieri remarks, after some other observations, that 

 the colours farthest from the spot heated, are those first formed, 

 and the nearest the last formed. Hence, the order in which they 

 should be considered is from the external ring inwards. The 

 first coloured zone is the largest, and it is larger as it is farther 

 from the heated spot. The coloured rings, also observed by 

 Newton between object glasses, and on soap-bubbles, vary in 

 size ; but with this difference, that they are always smaller as 

 they recede from the centre, whilst the metallic tints are larger 

 in the same situation. 



If, in similar circumstances, a greater number of series be 

 obtained, the zones are always narrower ; and when the number 

 is few, they are larger. 



When there is a succession of series, the first is composed of 

 dark yellow, dark red, dull purple, and dark azure, which passes 

 into sky-blue. The colours of this first series become obscured 

 by time, an effect not remarked as yet in the colours of the 

 other series. The green is wanting in it. 



The second series commences with yellow, then a fine purple, 

 a bright azure, and a fine gi-een. 



The third series is composed of yellow, purple, bright azure, 

 very narrow, and scarcely discernible, and then a dull green. 

 This series wants the blue. 



The fifth series has only two colours, purple and green, both 

 dull. It entirely wants the yellow. 



The sixth scries has also only two colours, purple and green, 

 but both dull. 



Vol. Vill. 2B 



