been given, and also the appellation of Azoic, because they contain no traces of plants or animals, and are therefore without life, or destitute of organic remains.

Above these formations lie the Secondary and the Tertiary formations.

II. The Secondary formations have been divided by Professor Ansted into three periods, the Older, the Middle, and the Newer Secondary.

1. The Older Secondary formation he again
divides into the Older Palæozoic period,
namely, 1. The Lower Silurian rocks,
to which the name of Protozoic has been
given, because they contain the first
traces of life; and, 2. The Upper Si-
lurian rocks, the Middle Paleozoic pe-
riod, containing the Devonian or Old
Red Sandstone formation; and
The Newer Palæozoic period, including,
1. The Carboniferous formation; and,
2. The Magnesian Limestone, or Per-
mian formation, and above these strata
lie-

The Upper New Red Sandstone or Triassic formation, the last member of the older secondary period.

2. The Middle secondary formation, consists of the Lias, Oolite, and Wealden formations; and,

3. The Newer secondary period consists of the Cretaceous or chalk formation.

III. The Tertiary formation consists, reckoning from below, of,—

1. The older tertiary, or Eocene, viz., Bagshot sand and London clay.

2. The middle tertiary, or Miocene, viz.,
Red and Coralline Rag.

3. The newer tertiary, or Pliocene, viz.,
the Till of Clyde and Norwich Crag.
4. The superficial deposits, or Pleistocene,
viz., all diluvial and alluvial deposits of
gravel and other materials, sometimes
stratified.

The proportional thicknesses of these different formations have been estimated by Professor

Phillips as follows, but the numbers can be regarded only as a very rude estimate:

Thickness of the Earth's crust, 46,600 9 miles nearly.

=

As all the stratified formations which compose the crust of the earth have obviously been deposited in succession, geologists have endeavoured to form some notion of the time occupied in their deposition, or the age of the most ancient of them. By studying the fossil remains found in the different formations, geologists have placed it beyond a doubt, that great changes have taken place during the formation of the crust of the earth. The plants and animals. which existed in one period are not found in another, new species were at different times created, and frequent convulsions have taken place, upheaving the beds of the ocean into continents and mountain ranges, and covering the dry land with the waters which were dis

placed. That the deposition of strata of such thickness, and operations of such magnitude, required a long period of time for their accomplishment, has been willingly conceded to the geologist; but this concession has been founded on the adoption of a unit of measure which may or may not be correct. It is taken for granted, that many of the stratified rocks were deposited in the sea by the same slow processes which are going on in the present day; and as the thickness of the deposits now produced is a very small quantity during a long period of time, it is inferred that nine or ten miles of strata must have taken millions of years for their formation.

We are not disposed to grudge the geologist even periods so marvellous as this, provided they are considered as merely hypothetical; but when we find, as we shall presently do, that speculative writers employ these assumed periods as positive truths, for establishing other theories which we consider erroneous, and even dangerous, we are compelled to examine more minutely a chronology which has been thus misapplied.

Although we may admit that our seas and continents have nearly the same locality, and cover nearly the same area as they did at the creation of Adam; and that the hills have not since that time changed their form or their height; nor the beds of the ocean become deeper or shallower from the diurnal changes going on around us, yet this does not authorize us to conclude that the world was prepared for man by similar causes operating in a similar manner. The same physical causes may operate quickly or slowly. The dew may fall invisibly on the ground, the gentle shower may descend noiseless on the grass,-or the watery vapour may rush down in showers and torrents of rain, destroying animal and vegetable life. The frozen moisture may fall in atoms of crystal, which are felt only by the tender skin upon which they light; or it may come down in flakes of snow, forming beds many feet in thickness; or it may be precipitated in destructive hailstones, or in masses of ice which crush everything upon which they fall.

When the earth was completed as the home of the human family, violent changes upon its surface were incompatible with the security of