Iron * 
07 
at the temperature of 60 of Fahrenheit’s thermometer., 
No w as 44 grains of chalk will yield air, equal to that 
bulk of water, one pint of air will designate 44 grains of 
pure limestone. This can be done by fixing a tube of 
tin, or copper, or glass, bent like the letter S into a cork. 
Insert the cork in the bottle or vial which contains veur 
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mixture of spirit of salt and water with the ore to be tried® 
Invert the pint decanter full of water in water, and let the 
air displace the water of the inverted decanter. 
Having thus ascertained the quantity of limestone if 
any, you will have a guide how much to add, when you 
know the proportion already contained in the ore. If the 
ore be, as it often is, an argillaceous ore, which can be 
toid by putting your tongue to it, which will adhere ; 
or by the earthy smell perceived on breathing on it, it will 
require more limestone in proportion to the clay. Calca- 
reous ores and siliceous ores, do not emit an earthy smell 
or adhere sensibly to the tongue. 
If your ore be a calcareous ore, that is, inveloped in 
limestone, it would be absurd to use a limestone flux ; 
your flux should be half its weight of clay. If it be a sili- 
ceous ore it will require both limestone and clay. Nor is 
it the quantity of iron alone, that depends upon the due. 
mixture of the earths which are to form the flux : the 
quality and appearance of the iron produced, equally de- 
pend upon the same circumstance : and it may be safely 1 
taken for granted, that when an ore is well deprived by 
roasting of its sulphur or its arsenic, if there be any, and 
when the due proportions of coal for heating and metal- 
lizing, and of earths as a flux are known by well ascer- 
taining the component parts of the ore, every ore may be 
made to furnish the same kind of iron. 
Directions for assaying ores in the small way, by the 
same process that is employed in the large way, are given 
in die following papers of a practical and experienced iron 
