55 
Iron 9 
regular strata of iron-stone. To such a primary and se- 
condary agency of formation may be attributed the gene- 
ral superior richness of ores found in irregular vertical 
masses, to that of iron-stones. The same cause will also 
explain why more determinate qualities of iron are obtain- 
ed from primitive ores, than from those of a secondary 
formation. In the former, the mixtures are commonly 
fewer, and the quality of the malleable iron more decided ; 
in the latter, the quality of the metal is less certain, and 
more various, from the mixtures being more numerous,, 
Hence we may also trace the reason of the superior quali- 
ties and marks possessed by some of the foreign fabrics 
over each other, where the same fuel has been used, and 
the same course of manufacture followed. 
Having so far considered crude iron, in regard to its 
fusibility, and the facility with which it becomes changed 
into various degrees of carbonation or oxygenation, con- 
stituting a variety of qualities most pointedly distinguish- 
ed in commerce, and in which the metallurgist discovers 
widely different properties and charateristic forms ; I shall 
next proceed to mention in what manner strength may be 
given to any quality of crude iron which may probably be 
obtained by the fusion of an ore, and from what source 
this property is derived. 
Upon a former occasion I have mentioned that iron, ob- 
tained from argillaceous ores, possessed a degree of strength 
beyond that obtained from the other genera. This truth 
daily presents itself to our observation in the large scale of 
manufacture ; , and however erroneous the reasoning of the 
manufacturer as to the cause, yet so evident are the conse- 
quences produced, that we must immediately attribute 
them to some source beyond the casualities of operation 
in the smelting furnace. In the explanation of this fact, 
as on the degrees of oxygenation and carbonation in ge* 
fteral the manufacturer has recourse to the existent nature 
