[ «9 ] 
and, as foon as poflible, obferved it in the dark. As 
he expe&ed, it imbibed no Light. Upon pouring 
into it fome Oil of Tartar, it became turbid and 
whitifh, from the Well-Water being ufually impreg- 
nated with calcarious Matter. Upon obferving it 
then in the dark, after having been expofed as before, 
it retained enough of a pale Light to diftinguifh the 
Shape of the Bottle. In a Bottle of Rain-Water he 
diffolved fome Talcs which Stone, by rubbing, will 
diflolve in Water as Salts do, without rendering 
it opaque ; to this Solution he added Oil of 
Tartar, and this Mixture was luminous as the pre- 
ceding. He therefore concludes, that fo long as 
earthy Corpufcles are very fmall, feparate, and agree- 
ing in their Surfaces with the Water in which they 
float, they readily tranfmit the Light they receive j 
for which Reafon it is impoflible they fhouid retain 
Light enough to appear luminous in the dark. But, 
by the AfFufion of the faline Principle, the earthy 
Corpufcles unite with the Water and Salts and from 
the Union of thefe Principles the Mixture grows 
thick, whereby the ready Tranfmiffion of Light is 
prevented 5 fothat, if this Mixture is without Colour, 
or any thing metallic, the Light will be flopped long 
enough to be vifible in the dark. But if, inftead of 
Oil of Tartar, you add Sugar of Lead, the Mixture 
will be turbid, but retain no Light. In thefe two 
Experiments the Water becomes a 2° ho (p horns. 
Gems, Cryftals, and Glafs, whether whole, or 
powder’d ever fo fine, retain no Light j fo that nei- 
ther their Tranfparency nor Whitenefs contribute to 
their becoming luminous in the dark. Of feveral 
Diamonds, in all Appearance perfedlythe fame, fome 
M were 
y 
