the proportion^ of the component parts of the flux, the 
metal of the same iron-stone may be made to pass through 
all the inferior statesc 
Since, then, all iron-stones in the assay-furnace may be 
made to give out their iron at pleasure, of all the various 
qualit ies, it is surely erroneous to assert, that such and 
such iron-stones contain such and such qualities of iron ; 
that this one affords metal of the finest quality, while that, 
Qii the contrary, yields iron fit only for forge-pigs or bal- 
last ; yet this is the universal language in the manufacto- 
ry. In this, as in many instances, we accommodate the 
language to our ideas, rather than our ideas to truth. The 
suffrage of prevailing custom has imperceptibly associa- 
ted with our ideas many absurdities which we are after-, 
wards ashamed to acknowledge, and which darken the 
gleam of truth, or render it apparently ridiculous, merely 
because it is at varience with our prejudices. Where 
science guides not the manufacturer, or is scorned by 
him, his train of reasoning, though far from being just, is 
short ; it is fitted to the narrow culture of his mind, and con- 
sonant to a barbarous nomenclature of received usage 
* I cannot resist noticing one instance, prevalent at iron-works^ 
of that blind reverence to the opinion of our predecessors, whose 
sources of knowledge must necessarily have been few and contract- 
ed. When super-carbonated crude iron is run from the furnace, 
it is frequently covered with a scurf, which when cold is found to 
be a coating of plumbago (carburet of iron) remarkably brilliant ; 
sometimes in small specks, and at other times in large flakes ; ; 
this substance is universally denominated sulphur , and, as the most 
expressive adjective for that quality, we say that the iron is sulphu - 
ry«. There are not, perhaps, two substances so opposite in their 
degrees of inflammability, or so widely different in their properties, 
as sulphur and plumbago ; the existence of the latter almost whol- 
ly supposes a total absence of the former s yet, such is the want of 
investigation, or the slightest momentary reflection, that an indo- 
lent belief is passed as to the presence of a substance diametrically 
to that which, is. expressed. Sulphur has hitherto bee^. 
