C 55° ] 
4. They have a very different Way in the North 
of England of reducing their Kelp to Pot-afh, 
which they ufe for making Alum. This is made 
of the different Kinds of Fuel , or Sea-Weeds thrown 
up on the Shore, or gather’d on the Rocks * which 
they dry a little in the Sun, and afterwards burn 
them in a Kiln, built of the Stones they find on 
the Shore, in a cylindrical Form, and about two 
Foot or lefs in Diameter. In this they fird burn a 
fmall Parcel of the Herb, and before it is reduced 
to Afhes they throw on more, till the Kiln is full, 
or their Materials are expended. This is faid to 
reduce the Afhes to a hard and folid Cake, by the 
Heat of the Kiln, and Quantity of Salt in the Herb, 
which makes what is commonly called Kelp -Afhes 
There are fomc other Ways of making Pot-afh, 
fuggeded by feveral, both Authors and others, which 
appear to be more eafy and ready than any of the 
above-mentioned 5 for which Reafon they are apt to 
be tried by thofe who make Attempts of this kind. 
Thefe are deduced from what they reckon the Na-* 
ture and Properties of this Production : And there 
is no doubt, but if that was well underdood, it 
might afford fome Infight in the Way of making it.. 
For this Reafon we made the following Experiments 
with the beft RuJJia Pot afh, in order to difeover its 
Nature and Properties, and how they are mod pro- 
bably communicated to it j that we might fee what 
we are to make? in order to imitate the bed, or 
to make what is accounted good Pot-afh. 
1. Rujjia Pot-afh, as it is brought to us,, is in 
large Lumps, as hard as a Stone, and black as a 
Coal, 
