48 
Iron , 
beat all times the same, and the requisite heat conveyed and 
completed at similar stages of fusion and of separation 
Strict accuracy of result, as to the quantity of metal, will 
not always be obtained ; but a very comprehensive know- 
ledge will be formed of the nature of the earthy mixtures^ 
and the strength and fusibility of the metal. Once in the 
possession of these, it will be no difficult matter to super- 
add a portion of earths requisite for perfect reduction. In 
two simple experiments, therefore, not only the real qu en- 
tity of metal contained in the ore is obtained, but its pre- 
sumptive strength and fusibility developed in a great mea- 
sure prior to its application to the purposes of the blast* 
furnace.”* * * * 
‘ It will easily be conceived, from the mode of opera- 
tion which I have adopted, that, in order to procure accu- 
rate results, the proportion of flux must be varied accord- 
ing to the mixtures in the iron-stones or ores ; and that 
no universal solvent can be used as capable of assaying 
all ores. 
As the gradation of mixtures in the ores is almost im- 
perceptible, there are, in fact, no fixed limits by which 
Nature has distinguished the various classes : we find all 
the varieties diminishing their predominant earth, and as- 
suming, in equal proportions, those of each other, thus 
constituting the class of equalised mixtures ; yet, here, 
the variety of combination ceases not, the predominating 
earth gradually becomes the minor part of the mixture, 
and that which only held a second rank, as to quantity, is 
now the chief component earth ; the permutation goes 
round, till the earth, which existed in the most sparing 
. quantity, now predominates to excess. 
In such an infinity of variation, it is difficult to arrange 
the combinations of which these substances are capable. 
To derive the name of a class, or genus, from the predomi- 
nancy of an earth, seems most eligible ; and to consider 
