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light ethereal Oil, to make them appear luminous. 
But here great Care muft be taken that they boil no 
longer than from being white they turn yellow; for 
if you proceed longer, your Labour is loft. 
It is neceflary that you fhould be acquainted, that 
thofe Phofphori , which are produced by Torrefadion, 
foon lofe their Power, which, perhaps, neither Time, 
nor a thorough Diflblutionof their Parts, can deprive 
the natural ones of. In general, as long as the Phof 
phoriy gained by Torrefadion, preferve their Power, 
their Light is more {harp and ftriking, but the natu- 
ral, more weak. But thofe that are gained by Cal- 
cination, and Baldwyris Phofphorusy feem to pof- 
fefs both the ftriking Light of thofe gained by Tor- 
refadion. and the weaker Light of the natural Phof- 
phori: The laft they preferve a long time, but the 
former is loft by degrees much fooner. The well 
calcin’d Allies of Plants, or rather their terreftrial 
Parts remaining after the Solution of their fixed Salts 
by wafhing, and neutral Saits, continue Phofphori 
after many Years. So that, as far as we can judge, 
the luminating Power which is gained by Calcination, 
tho’ not fo intenfe, continues perpetual ; whereas 
that gained by Torrefadion always decreafes, and in 
a very little while is no longer vifible. Some even* 
by this Method, continue to imbibe Light much 
longer than others. Gum ArabiCy which continues 
longeft, lafts fix Days ; Bread, not one ; and Coffee* 
only a few Minutes. However, at any time, by a 
frefh Torrefadion, you may recover thefe languid 
Phofphori--, in which Property they have great Likenefs 
to the Bolognian Stone, and other Phofphori prepared 
by Art, The Phofphori gained by Torrefadion, as 
well 
