47 
Iron , 
judgment of the tendency which individual ores have to 
afford their metal carbonated, possessing strength, or 
otherwise, a flux of a medium proportion of calcareous 
earth and glass is determined upon ; such as, with an iron- 
stone of that genus, would afford super- carbonated crude 
iron. Let the button of iron so obtained be the standard 
whereby to judge of succeeding results ; and let all the 
ores belonging to the same mine, or used at the same work, 
be compared with it : these will be found, according tg 
their mixtures, possessing different degrees of carbona- 
tion ; some of them white in the fracture, and others again 
as richly carbonated as the standard regulus ; their degrees 
of strength also approaching or receding from the standard 
as they approximate or vary from the nature and propor- 
tion of its original mixture. 
To complete such an undertaking with accuracy, re- 
quires a minute knowledge of the operations of the assay- 
furnace, and the degree of heat from time to time excited : 
the quantity of ore in such a chain of experiments should 
how far and in what manner the mechanical structure of the metal 
is altered when additional strength is thus obtained. It will be a dif- 
ficult matter to decide, whether it is derived from the natural infu- 
sibility of the clay, by preventing separation for a longer time, and 
new modifying the structure of the particles of metal ; or whether 
the acquired strength is entirely owing to the moleculse of the me- 
tal becoming more flattened and tenacious by a varied stage of crys- 
tallisation. Most probably it is owing to both causes, and that the 
former is productive of the latter ; the one the cause, and the 
other the effect accounted for. 
We find, that from siliceous iron-stone, which is fused with the 
greatest facility, iron is obtained uncommonly white and brittle; 
and again, from pure calcareous iron-stones, which are still more 
difficult to reduce than tne other two classes, we find an opposite 
extreme of brittleness, arising from an extra combination of carbon, 
which destroys the continuity of the particles to each other. Clay 
stiL no Ids tne medium ; and its addition alone restores a just 
equilibrium, not of strength only, but of fusibility. Mushet. 
