8 
such rules must be relaxed, and that greater weight must be 
attached to those substances, chemically impure though they 
may be, which are abundantly yielded by our mines and quarries, 
and yet scarcely constitute true mineralogical species. 
We shall thus, for example, study the characters of the pure 
carbonate of iron in the crystals occasionally lining the cavities 
of our lodes, in the masses which exert so powerful an influence 
on the industry of Nassau and the Austrian Alps, and again in 
those indefinite mixtures which as nodules and continuous beds 
have, from their geological position and abundance, contributed 
in a high degree to raise Great Britain to her present pinnacle 
of manufacturing power. 
But the cause of such a preference in mineralogical works is 
at once evident, on comparison of the objects described with 
those of the other classificatory sciences. 
In the animal and vegetable kingdoms the naturalist traces, 
in successive groups of animals and plants, a descending scale of 
lower and lower organization, till at last, in the most rudimen- 
tary forms of life, individuality is lost in an assemblage ; yet 
down to this point each species presents none but forms complete 
in themselves, and almost unvarying. In the mineral kingdom, 
on the other hand, we are obliged to seek out for description the 
most perfect specimen, because it is not a succession of species, 
but the same species which offers a never-ending diversity of 
aspect. The mineral species may indeed occur in every state of 
development, from the symmetrical crystal, composed of definite 
constituents, passing through every grade of incompleteness of 
form or admixture with foreign substances, till we reach the 
lowest step of the scale, where the individual is so mei'ged in the 
mass that form is destroyed, and the other characteristics are no 
longer discernible to the sense. How striking is the parallel in 
human societies, where the development of mind and resources 
unmistakeably accompanies such arrangements as lead to the 
self-reliance and importance of the individual, whilst as surely 
the crippled freedom of action caused by merging individuality 
in the crowd is attended by deterioration and destruction of all 
healthful prominences of character ! 
But besides the miner, there are hundreds and thousands 
