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Gum, are unfit for Pot-afh, as their Afhes arc well 
known, even to our Planters, to make a very weak 
Lye, unfit for Soap. 
Befides thefe that contain little or no Salt, there 
are fome other Vegetables that afford a large Quan- 
tity of it, but make a bad kind of Pot-afh, at leafl 
for many Purpofes, on account of a neutral Salt 
with which they abound. This feems to have been 
the Cafe of the Pot-afh made in Africa , in a Ma- 
nufacture of that Commodity fet up there by the 
African Company, which Mr. Hoiifton (who was 
chiefly concerned about it) tells us, in his Travels , 
proved fo bad, on account of a neutral Salt it con- 
tained, that the Manufacture was left off on that 
account; or, perhaps, from their not knowing how 
to make it aright. What thofe Vegetables are, 
that afford this kind of Afh, is not well known, 
if it be not Fern, and fome Sea- Plants. 
Whatever Vegetables we make our Pot-afh of 
fhould be frefh or green, and no ways rotten, dried, 
or decay’d. They fhould likewife be burnt to 
Afhes by a flow Fire, or in a dole Place j other- 
wife, when they are burnt in the open Air by a 
ftrong Fire, great Quantity of the Afhes is con- 
fumed in Smoke, by the faline and terreftrial Parts 
being carried up in Fumes, before they are feparated 
from thefe exhalable Parts by the ACtion of the 
Fire. For the Difference between burning Wood 
in a clofe Place, or the open Air, is fo great, that 
the Quantity of Afhes obtained from one is more 
than double the other. This we learn from the 
Experiments of Lundmarck hereafter mention’d, 
who tells us, he burnt a Quantity of Birch in a 
clofe 
