394 Royal Institution. 
Mr. Davy, “can: scarcely ever want objects of employ- 
ment. and of interest, 
“<The ground:on which he treads, the country which sur- 
rounds him, and even the rocks and stones removed from 
their natural position by art, are all capable of affording 
some degree of amusement—and every new mine or quarry 
that is opened, every new surface of the earth that is laid 
bare, and every new country thatis discovered, offers to him 
novel sources of information. 
‘¢ Tn travelling, he is interested in a pursuit which must 
constantly preserve the mind awake to the scenes presented 
to it—and the beauty, the majesty, and the sublimity of the 
great forms of nature, must necessarily be enhanced by the 
conteinplation of their order, their mutual dependence, their 
connexion as a whole. 
‘<The imagery of a mountain country,.which is the very 
theatre of the science, is in almostiall\cases highly impres- 
sive and delightful ;..but a new;.and,a.nobler species of en- 
joyment arises-iticthe mind, when the, arrangement. in it, 
its uses, and its subserviency to life are considered. 
‘To the geological inquirer, every mountain chain offers 
decided proofs. of the great alterations that the globe has 
undergone.”’, ., Meant 
Lecture 1.—In this lecture Mr.,Davy described two 
species of characters to be attended to in the study of geo- 
logy—one, those which insulated specimens of rocks pre- 
sent, such as. physical qualities, constituent parts, &c. the 
other, the aspect of rocks considered as great masses, or their 
general features, such as outline from colour, stratification, &c. 
_ In the primary order of rocks, he pointed out and de- 
scribed six classes,. These, he observed, included al} rocks 
strictly belonging to this order. . He excluded argillaceous 
and siliceous schist, because water-worn stones or shells 
occur in them, and the topaz rock of Werner, as having 
more the appearance of part of avein. Granite, micaceous 
schist, sienite, serpentine, porphyry, and marble, are primary 
rocks.—All these arrangements are constituted by a few 
crystalline substanees, which are principally quartz, feld- 
spar, mica, hornblend, talc, and calcareous spar. Thus 
granite is an aggregate of crvstal, of quartz, mica, and feld- 
spar, and siemite of quartz, feldspar, and hornblend—mi- 
caceous schist, of quartz and mica—serpentine, of skiller 
spar, talc, ana feldspar, containing veins of steatite. 
The mechanical constituents of rocks are few; but their 
chemical elements are still Jess numerous. When sub- 
jected to analytical processes, they afford silex, alumina, 
magnesia, 
