66 



All these deposits require and result from the destruction of other and 

 older deposits, by the action of atmospheric agents, such as rain, frost, running 

 ■water, and ice or glaciers. Now the ground we stand upon, nourishing grass 

 and trees, requii-es a long time for its accumulation by almost imperceptible 

 degrees, through the decay of lichens, mosses, and such scanty vegetation on the 

 surface of rocks, sands, and clays left by the waters. By slow degrees the 

 barren surface is covered by a bed of some inches of dark brown soil, or loam as 

 we call it, which is capable of cultivation. But below this soil we come to the 

 sedimentary deposit of the district, whatever that may be. The most recent forms 

 of this are seen in deltas at the mouths of great rivers, such as the Nile, or the 

 Mississippi, and on the margin of such coasts as have been raised above the sea in 

 comparatively recent times. 



I ought to have mentioned that though the sedimentary strata have all been 

 originally horizontal, or nearly so, yet by a beneficent disposition of Providence 

 the action of earthquakes and volcanoes, or other causes which are not yet 

 sufficiently understood, has elevated portions of them, and tilted them more 

 or less upon their edges, thus exposing them to the action of weather and water, 

 which have removed vast thicknesses of them, and thus enabled us to obtain coal, 

 which is so essential to us, but which was originally covered by too vast a thick- 

 ness of other beds, to be attainable by man. Indeed he could never have known 

 of its existence, without this elevation. 



These recent sedimentary beds contain in many places the remains of man, 

 together with those of existing animals, but yet are of very great thickness in some 

 places, such as the Nile, and must have required vast time to accumulate, since 

 we must refer them back to the age of the earliest Egyptians at least. In other 

 cases we find deposits of this age in the form of drift or gravels, as in the valley of 

 the Somme at Amiens, where it forms a terrace, elevated 300 feet above the present 

 level of the river ; and in the deposit of glacial drift on the top of Mount Tryfaen, 

 in Carnarvonshire, at the height of 1,400 feet above the sea. IMany of these old 

 gravels and river deposits contain the remains of quadrupeds which are now 

 extinct, such as the great Irish Elk, the Mammoth, &c. Indeed I have myself a 

 molar tooth of the Mammoth, which was found in the gi'avel at Wooferton 

 Kailway cutting. You must admit that the date of the existence of these animals 

 must have been long ages past, yet these formations are called recent, or post- 

 tertiary, and the shells contained in them are all of existing species. 



Below these recent beds come a long series of formations, deposited in 

 many places successively upon one another, which are denominated Tertiary, and 

 which are divided into three great classes — the Pliocene, or most recent, — the 

 Miocene, or less recent, — and the Eocene, or dawn of existing life. In the Plio- 

 cene, we find from 10 to 40 per cent, of shells of extinct species ; in the Miocene 

 the proportion of extinct shells varies from 60 to 80 per cent. ; in the Eocene 

 almost all the shells are unknown at the i^reaent time in our seas, and the 

 remains of plants found inilicate a tropical climate. What an immense length of 

 tima must have elapsed since that state of things existed ! And yet this is but 



