( * 99 ) 
yet it does not give it- near fo much attractive 
Force. 
Becaufe common black Soap is made of Oil boiled 
with a Lixivium ofPot-alh,Ihad a mind to try whe- 
ther Soap might not do more than Salt alone in raif- 
ing the Virtue in the Sand ; fo I mix’d the Sand 
with an equal quantity of Soap, which I firft ex- 
pos’d to a gentle Fire in an open Crucible, to dry up 
the Soap which fwells very much ; then the Fire 
was encreas’d for three quarters of an Hour, all the 
oily Subftance wholly confum’d, and the Matter in 
the Crucible was ftrongly fir’d ; then afterwards 
boiling it in Water, and walhing it well, I obtain’d 
a black Sand , which was all endued with a lively 
attracting Force. Very well pleas’d with this Sue- 
cefs, I had a Mind to try whether I might -raife a 
greater Force in it ; wherefore I again roafted it with 
black Soap as before, and even a third Time ; but 
no Addition was thereby made to its Virtue: I find 
that flaying too long in the Fire is as prejudicial as 
flaying too fliort a Time, between half an Hour 
and an Hour feem’d to me the moft proper fpace of 
Time. 
After, I added to the black Soap half of Salt of 
c f artar, and mix'd thereto an equal quantity of 
Sand ; which, when it had been expofed to a rever- 
beratory Fire - of an Hour in a Crucible, I walh’d in 
Water ; and then fo great was the Virtue of the Sand, 
that if it did not exceed the former, at leaft it was 
equal to it. 
Becaufe I had obferv’d the Oilinefs of the Soap to 
conduce much to excite the Vertue in the Sand ; I 
R r mix’d 
