to show the manner in which all stratified rocks have at various periods been disturbed, by the intrusion of unstratified crystalline rocks; and variously affected by elevations, depressions, fractures, and dislocations; fourthly, to give examples of the alterations in the forms of animal and vegetable life, that have accompanied these changes of the mineral conditions of the earth.
From the above section it appears that there are eight distinct varieties of the crystalline unstratified rocks, and twenty-eight well defined divisions of the stratified formations. Taking the average maximum thickness of each of these divisions, at one thousand feet,[1] we should have a total amount of more than five miles; but as the transition and primary strata very much exceed this average, the aggregate of all the. European stratified series may be considered to be at least ten miles.
CHAPTER IV.
Relation of Unstratified to Stratified Rocks.
I shall enter into no further details respecting the component members of each group of stratified rocks, than are represented by the lines of division and colours upon the section.[2] They are arranged under the old divisions of primary,
- ↑ Many formations greatly exceed, whilst others fall short, of the average here taken.
- ↑ For particular information respecting the mineral character and organic remains of the strata composing each series, I must refer to the numerous publications that have been devoted to these subjects. A most convenient summary of the contents of these publications will be found in De La Beche's Manual of Geology, and in Von Meyer's Palæologia, (Frankfurt, 1832;) ample details respecting the English strata are given
