SECOND REPORT — 1832 * 
From the nature of this portion of mineralogical study, it is 
scarcely susceptible of much speculative progress. The in¬ 
crease of the personal skill and sagacity of the observer by 
practice is the best result of its cultivation. Yet some improve¬ 
ments in method may be pointed out as having been recently 
made. Werner, eminently acute in his observation of sensible 
qualities, gave fixity to his discriminations by the introduction 
of an appropriate nomenclature. His pupil Mohs, formerly his 
successor at Freiberg, and now Professor at Vienna,—one of the 
most gifted of his disciples in the same way,—has attempted to 
fix one of the most important characters, hardness, by a nu¬ 
merical scale. In this scale, the hardness of common talc is 1, 
of gypsum 2, of calc spar 3, of fluor spar 4, of apatite or aspa¬ 
ragus stone 5, of felspar 6, of quartz 7, of topaz 8, of corun¬ 
dum 9, of diamond 10 thus, to say that the hardness of a 
mineral is 5J indicates that it scratches apatite and is scratch¬ 
ed by felspar. Prof. Breithaupt of Freiberg, the pupil and 
successor of Mohs, has proposed to put 12 degrees in this scale 
instead of 10, introducing mica between gypsum and calc spar, 
and sodalite between apatite and felspar, as intermediate de¬ 
grees. It has been observed by others, that the hardness of seve¬ 
ral minerals is different in different parts, and even in different 
directions ; thus kyanite gives a different value of the hardness, 
according as we scratch it along or across the direction of the 
axis. 
The specific gravity has also been scrupulously attended to 
by the same school of mineralogists, and both Mohs and Breit- 
haupt have determined very minutely the value of this element 
for very extensive series of minerals. Beudant also has paid 
great attention to this subject; he has ascertained by expe¬ 
riment (1. x. 331.) that large crystals, and especially bacillary 
masses, have a smaller specific gravity than small crystals ; 
and he hence recommends us to reduce minerals to powder 
previously to finding their specific gravity, in order to avoid the 
influence of these differences in the mode of aggregation. 
Magnus found that garnet and similar minerals when melted 
and again solidified in a glassy but uncrystalline state have their 
density diminished ; the Greenland garnet, for instance, was in 
this manner reduced from sp. gr. 3*9 to 3*()<>. 
In the observation of the colour and lustre of minerals, we 
have hitherto been left to the unassisted eye and judgement. 
It was the object of an instrument described and exhibited by 
Sir David Brewster, at the last Meeting of the British Asso- 
ciation, to make this observation more precise and delicate. 
The principle of the instrument is, to observe, not the whole 
light reflected from the surface of the mineral, but the excess 
