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water; a solution of nitre did not increase it 

 quite so much. Sal-ammoniac diminished it a 

 little, oil of tartar, per deliquium, nearly extin- 

 guished it, and the acids entirely. This water 

 poured upon fresh calcined gypsum, rock crystal, 

 ceruse, or sugar, became more luminous. He 

 also tried the effects of it when poured upon 

 various other substances, but there was nothing 

 very remarkable in them. Afterwards, using 

 luminous milk, he found that oil of vitriol extin- 

 guished the light, but that of tartar increased it. 

 This gentleman had the curiosity to try how 

 differently-coloured substances were affected by 

 this kind of light; and having, for the purpose, 

 dipped several ribbons in it, the white came out 

 the brightest, next to this was the yellow, and 

 then the green ; the other colours could hardly 

 be perceived. It was not, however, any parti- 

 cular colour, but only light, that was perceived 

 in this case. He then dipped boards painted 

 with the different colours, and also glass tubes 

 filled with the substances of different colours, 

 in water rendered luminous by the fishes. In 

 both these cases, the red was hardly visible, the 

 yellow was the brightest, and the violet the 

 dullest. But on the boards, the blue was nearly 



