I(j6 - Ori the Jffiint'ies of 



years ago, through the medium of this publication, to ar- 

 ran<z;e our iron-stones, generally denominated " secondary 

 argillaceous ores of iron," into four classes, viz. calcareous, 

 argillaceous, siliceous, and class of equal mixtures. I have 

 since added to these, three new classes, not hitherto, I be- 

 lieve, acknowledged as iron-stones, viz. carbonaceous, bi- 

 tuminous, and granulated : the two former classes, if ever 

 examined or suspected as belonging to the varieties of se- 

 condary ores, were either considered as coal or rejected as 

 whin stone. Analysis, however, by the separation of a 

 hirge portion of metal from each, taught me to value ihem 

 accordingly, and to rank them as real secondary ores of iron 

 possessed of new and interesting features. 



Of the tirst four classes, the varieties chiefly used at iron- 

 works are those of the class I have styled " equal mixtures." 

 But as the combination of lime, clav, silex, nxni, and oxy- 

 gen, is susceptible of an almost endless variety of modifica- 

 tion before any one earth exclusively predominate, even the 

 same class of ores may in their results afford a similar va- 

 riety in the peculiar or native properties of the metal which 

 it contains. Under this class we find numerous modifica- 

 tions of calcareous earth crystallized, in the state of spar, 

 on marine remains, disseminated, or in chalky lines parallel 

 or mtersccting each other throughout the fracture of the 

 ore. 



The next supply in point of quantity is derived from the 

 aroillaceous ore ; but there are but few varieties of this class 

 that approach to any great degree of purity. 



Calcareous iron-stone in its purest state is extremely 

 scarce, and is as yet no where found in quantity excepting 

 upon the Whitby and Scarborough coast. Its appearance 

 beinf very different in point of colour from common iron- 

 stones renders it an object of suspicion to the iron-master 

 in general ; and there are but few varieties hitherto that 

 have been permitted to enter the precincts of the turnace- 

 yard. The union of lime, however, in the common quali- 

 ties of iron-stone forms a striking and interesting character, 

 which is frequently beiieficially felt by admitting a reduc- 

 tion of that quantity of lime-stone in the furnace which 

 ore highly argillaceous would require. 



The siliceous class of iron-stones seldom or ever form 

 any part of the supply of the manufacture)', and I believe 

 their existence in a state comparatively pure is equally un- 

 known to him and the mineralogist. In general it may be 

 remarked, that at all iron-works iron-stones containing a 

 lar""cr proportion of sand than common are carefully re- 

 jected. 



