Principles of Geology. 9 
clay, chalk, and other strata of inferior hardness, and not crystallized, 
but amply stored, nay filled to admiration, with plants, corals, shells, 
and other remains of organized beings. Besides these, there is a 
third division of rocks; viz. sienite, porphyry, basalt, &c. which are 
of local occurrence, appear in peculiar forms, and present particular 
phenomena. They repose indiscriminately upon the rocks of the 
mountains or those of the plains, and occasionally divide them by 
dykes, yet have only an accidental connexion with either. Such is 
the general character of the geology of Britain. And I may appeal 
to the progress of the science for proof, that such is the general char- 
acter of the whole face of the earth. BOGS 
In every country the great mountain ranges are composed of the 
lowest rocks with which we are acquainted. ‘There may be other 
rocks below the granitic series, but we have not yet found means to 
observe them. Therefore, as being the lowest, and consequently the 
Most ancient rocks, included in the compass of our observation, we 
call them Primary. Those more horizontally deposited rocks which 
fill wide plains, and rest upon the subterranean slopes of the former 
series, composed of various alternations of calcareous, siliceous, and 
argillaceous substances, with local deposits of coal, and generally 
abounding in shells and other organic remains, are universally termed 
Secondary. Those rocks which rest indiscriminately on the primary 
or the secondary series, lie in irregular patches, and send off veins 
or branches into both primary and secondary, being in fact super- 
added to both, yet conjoined to neither, receive the name of Inde- 
pendent or Overlying. 
x a Frezp from theoretical views, or rather under the influence of very 
Opposite and Contradictory theories, all parties confirm this relation 
of facts, and agree in the conclusion, that the earth exhibits every 
Wiere the same principles of structure. It is now universally ad- 
mitted, that, to as great a depth as we can ascertain, our planet is 
“omposed of various but definite rocks, possessing constant charac- 
acters, whereby they may be distinguished, and that they are ar- 
*anged upon one another in a constant relative order. 
Ane mode of investigation by which this result has been obtained, 
“pears to me satisfactory. Beginning at home, we find certain reg- 
ularity of Structure to prevail; extending our views, we perceive 
“hat the rocks of our district are not insulated deposits, but portions 
ou. XXI.—No, 1. | 
