189 
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 chrystal, ceruss, 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 extinguished the light, but that oil of tartar 
increased it. 
This gentleman had the curiosity to try how differently coloured sub¬ 
stances were affected by this kind of light; and having, for this 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 per¬ 
ceived. It was not, however, any particular 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 substances of the 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 equal to the yellow, and the green more 
languid; whereas in the glasses, the blue was inferior to the green. 
Of all liquors into which he put the pholades, milk was rendered the most 
luminous. A single pholas made seven ounces of milk so luminous, that 
the faces of persons might be distinguished by it, and it looked as if it was 
transparent. 
Air appeared to be necessary to this light; for when Beccarius put the 
luminous milk into glass tubes, no agitation would make it shine, unless 
bubbles of air were mixed with it. Also Montius and Galeatius found, that, 
in an exhausted receiver, the pholas lost its light, but the water was some¬ 
times made more luminous; which they ascribed to the rising of bubbles of 
air through it. 
Beccarius, as well as Reaumur, had many schemes to render the light of 
these pholades permanent. For this purpose he kneaded the juice into a kind 
of paste, with flour, and found that it would give light when it was immersed 
in warm water ; but it answered best to preserve the fish in honey. In any 
other method of preservation, the property of becoming luminous would not 
continue longer than six months, but in honey it lasted above a year; and 
then it would, when plunged in warm water, give as much light as ever it 
had done before. 
3 B 
