MULTIVALVES. 95 
men, especially to M. Reaumur and M. Beccarius, 
who particularly devoted their attention to the sub- 
ject of phosphoric light. 
The luminous quality of the Pholas is in proportion 
to its freshness; but even when in a dry state, this 
quality may be revived by the application of fresh or 
salt water; but brandy immediately extinguishes it. 
A solution of sea-water increases the light of the 
luminous fluid; sal ammoniacum diminishes it a 
little; oil of tartar nearly extinguishes it, and the 
acids entirely. The luminous water, when poured 
upon fresh calcined gypsum, rock crystal, or sugar, 
becomes more vivid. Milk rendered luminous by the 
Pholas, loses its shining quality when mixed with oil 
of vitriol; but again revives it on the addition of oil 
of tartar. 
Differently coloured substances are powerfully 
affected by this kind of light: white appears to im- 
bibe and emit the greatest quantity; yellow and green 
in less proportions. Such is also the case with 
painted boards and glasses, when submitted to the 
same experiment. In both, the red will emit hardly 
any light—the yellow the most—the violet least 
of all. 
A single Pholas will render seven ounces of milk 
so beautifully luminous, that surrounding objects are 
rendered visible by its light. This luminous quality 
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