FORMATION OF COAL. 



115 



but, what is remarkable, this stem passed through three strata of 

 sandstone, parted by regular strata seams. It had, therefore, evi- 

 dently grown in the situation where it stood ; for it is difficult ta be- 

 lieve that any vegetable stem could pierce through three strata of 

 sandstone, the lower of which at least must have been partly con- 

 solidated. When we consider that these were the stems of hollow 

 tubular plants, equisetums, without any woody support, it is impossi- 

 ble to believe, that they could have remained erect in a warm tem- 

 perature, even for a very limited time, without speedy destruction 

 or decomposition. We are therefore certain, that they were speed- 

 ily encased in the strata that now surround them, or, in other words, 

 that three strata of sandstone nine feet in thickness were rapidly de- 

 posited. 



The coal mines at St. Etienne, in France, present similar appear- 

 ances; the vertical stems are numerous, and ten or twelve feet in 

 length. From a drawing and description of them given me by M. 

 Alexandre Brongniart, it appears, that they were large equisetums, 

 and the hollow tube is filled with sandstone. The circumstances, and 

 the inferences from them, agree with those before stated of Burnt- 

 wood quarry. 



In the section of the Ashby-de-la-Zouch coal, given below, it will 

 be seen, that there are no less than sixteen strata of blue-bind, ex- 

 actly of the same thickness, and alternating with sixteen strata of 

 ironstone, of which the six upper are only one inch in thickness, and 

 the lower two inches. If we should suppose each stratum of bind 

 and ironstone to have been deposited in different parts of one year, 

 we should have a speedy formation of these thin beds. We know 

 nothing, however, certain, respecting the formation of ironstone ; but 

 it appears to have been deposited in fresh water, as it occurs in fresh 

 water strata in the regular coal formation, and in the coal strata of 

 the oolites in Yorkshire, and among the clay and sandstone strata, in 

 the wealds of Kent. Few geologists have attempted to explain the 

 formation of ironstone. It may have been a deposition from cha- 

 lybeate waters, or was, perhaps, the produce of decomposed vegeta- 

 tion, as bog or peat iron is supposed to have been. 



Some geologists are of opinion, that coal was formed from peat; 

 but the fossil vegetables in coal strata, and in the coal itself, are not 

 what compose the peat of the present day. However, if northern 

 latitudes had the temperature of tropical climates during the geolo- 

 gical epoch when the vegetables flourished that are found in the 

 coal strata, the peat of that period would partake of a different char- 

 acter from recent peat beds, and might be produced by the rapid 

 decomposition of the large terrestrial and marsh plants, before re- 

 ferred to. A bed of modern peat, seven feet in thickness, is said 

 to have been formed in thirty years ; but the primitive vegetation of 

 the world, flourishing and decaying under a high degree of temper- 

 ature, and a moist atmosphere, might form thick beds of peat in a 

 much shorter period. 



