S^LT ox ^SHES^ 
Of a 
TIN or LE^T> OVEN. 
Our Porcellan Bakers ufe much tin, ox Z^^^which they 
calcine in their Oven's. This work (which they continue 
lo on 2 days together,that they may have a good quanti- 
ty of materialls by them, and not be forced to repeat the 
c3peration2 or times a monthj is lo prejudicial! to 
thofe that tend it, that a mau can't ftand before the 
mouth of the Oven, above 24 hours at a time, and then 
he looks as if he were poyfoned : fo that every day 
frefhmanis imployed, to take care of the Oven, and 
remove the fcum from the furface of the Lead. Thc^ 
confideration thereof, moved me to examine fome ofc 
that grayifh fubftance, which (ticks to the ftones, upoiL 
which the flame of the Oven beats; having diflblvedit 
in water, and let it ftand to fettle, I found feveralob* 
long figures, as Numb, 10. Fig^ -^. they were of dif* 
ferent magnitudes, and fome bigger then Fig* fome 
were fharp at both ends as Fig. C, All thefe, whether they 
fwam in the water, or lay out of it, were generally 
without any difcernable thicknefs, and were as tranfpa*^ 
rent as the cleareft water. 
I particularly obferved, that three figures, two of 
and one of lay in a quantity of water not fo big as a 
Sand : while I cauled iome heat in this water, and con*, 
tinned to watch it, as imagining the other Salts therein^; 
contaii'ied, would increafe the bulk of thele three> I 
could find nothing, but very fmall fquare Salts> whoi©,^ 
tides roie up Pyramidally ^ thefe indeed grew bigger^, 
but the others C and i)> were not altered ; as the fquare^" 
Salts grew bigger^ they became fo much the more irregu- 
