48 
[Assembly 
duetion of the metal. In order to facilitate the operation, sub- 
stances are added which are denominated Jiuxes, the use of which 
is to bring the earthy matters mixed or combined with the oxide 
of iron to a state of thin fusion or liquidity, so that the particles of 
metallic iron, having been formed by the action of the carbon, may 
run together and fall down to the bottom of the furance. It is evi- 
dent, therefore, that the nature of the flux must differ with that of 
the ore. When silicious matter predominates, limestone is used, 
so that the silica may form with it a fusible compound, and thus 
liberate the metal. On the contrary, when an ore contains car- 
bonate of lime, this substance being also infusible, a silicious flux 
is then to be employed.* 
From this view of the nature and use ©f fluxes, it is apparent 
that they cannot be employed in an arbitrary or empyrical man- 
ner. The particular kind, as well as the proportion, must be de- 
termined by the chemical composition of the ore; and it is very 
seldom that two ores so closely resemble each other as to allow 
the use of exactly the same flux. 
With the exception of the lenticular argillaceous oxide of the 
western part of the State, and the magnetic iron from Warrens- 
burgh, all the ores which I have examined are silicious or alumi* 
nous, and require for their reduction a flux composed chiefly of 
carbonate of lime. A limestone very highly esteemed for this pur- 
pose is obtained in Putnam county. It is white, granular, and so 
friable that it may be easily crushed by the fingers. Its composi- 
tion in 100 parts is as follows: 
Carbonic acid, 43.50 
Lime, 65.75 
Silica,.. 0.75 
100.00 
It is therefore nearly pure carbonate of lime, and it probably 
owes its superiority to its being so friable and granular. Another 
limestone, compact, and of a bluish colour, found in various parts 
of Dutchess county, is also devoted to the same use, and is in good 
repute. It contains from three to five per cent of foreign matter, 
principally silica. 
* On this subject I would refer to Dr. Colquhoun's Memoir, already quoted. 
