88 GEOLOGY. 



inch to 30 feet thick. Coals are evidently of vegetable 

 origin : leaves and stems of plants, and sometimes trunks 

 and branches of trees, are found in coal fields, partially 

 converted to coal. Whole forests may have been, in 

 certain instances, overturned by some extraordinary 

 action ; and the mass, by being pressed by a vast super- 

 incumbent weight, and exposed to a high temperature, 

 may have produced this most useful fuel. In many in- 

 stances, coal fields may have been formed from vast 

 masses of vegetable matter carried down into estuaries 

 and seas, with soil, and sand, and clay, and have become 

 arranged as we find them. The Mississippi, the Oroo- 

 noka, and other large rivers, carry annually into the 

 ocean immense masses of vegetable matter, which are 

 forming deposits to a vast extent. 



As we know that a very great part of England, as 

 well as the continent, was at one time underwater, those 

 very parts where the coal fields are might have been so, 

 and have been subsequently upheaved from the sea, or 

 they might have become dry land, by the seas retiring. 

 Under any circumstances, an immensity of time must 

 have been required to form this group. 



Providence has made a most wise arrangement in 

 regard to the coal strata, by causing rich beds of iron 

 ore to be contiguous to the coal beds and mountain lime- 

 stone, which latter is used as a flux for smelting the 

 iron.* After the deposition of these strata, and before 

 the superjacent rocks were formed, great derangement 

 took place by some violent internal action, producing 

 what the miners call /aw/ft, so that the seam of coal will 

 suddenly terminate by the other part being either sunk 

 down, or raised up, which, in some instances, amounts 

 to as much as 3,000 or even 4,000 feet. 



MAGNESIAN LIMESTONE. This rock is so called, 

 from the quantity of Magnesia that enters into its com- 



* Dr. Buckland, in reference to this, observes: " The important uses 

 of coal and iron in administering to the supply of our daily wants, 

 give to every individual amongst us, in almost every moment of our 

 lives, a personal concern, of which but lew are conscious, in the geolo- 

 gical events of those very distant eras. We are all brought into im- 

 mediate connection with the vegetation that clothed the ancient earth, 

 before one half of its actual surface had yet been formed. The trees 



