REVIEWS. 53 



flora is, to a certain degree, destitute of the poetic attractions with which 

 the rest of the present work is enriched, this chapter is far from " present- 

 ing merely a bare enumeration of fossil plants with technical descriptions," 

 for the subject is rendered most interesting by the way in which local facts 

 are used to illustrate scientific truths. In treating this subject the ap- 

 pendix opens with a well-digested sketch of the history of coal, viewed 

 under the several sub-divisions of relative position — origin, plants, or the 

 original materials of which coal was formed ; and, lastly, the changes which 

 coal has undergone, and the conditions of the era during which it was 

 deposited. Under each of these heads much useful information is con- 

 tained. From the first we learn : — 



" That true coal has been rarely seen amongst the oldest rocks ; the only in- 

 stance known to the author being that of an anthracite coal, six feet thick, in Por- 

 tugal, belonging to the lower silurian formation ; while the most remarkable coal 

 in the secondary series is a rich bituminous bed, 36 feet thick, in Eastern Virginia, 

 which Sir Charles Lyell has shown to be not more ancient than the lias formation. 

 But with these and a few other exceptions, productive or valuable seams of coal are 

 found only in that formation which lies between the old red sandstone and the new 

 red sandstone, and which has been called carboniferous, because a large amount of 

 carbon has been locked up in the coal and limestone bed. This conclusion is of 

 practical value, as enabling the geologist to point out the class of rocks which will 

 produce coal, and so prevent useless and expensive boring in formations which are 

 unproductive of coal seam." 



We would gladly extract the entire of the last of these sub-divisions ; 

 we have, however, space only for one passage, illustrative of the conditions 

 of the era during which the coal formation was deposited : — 



" The complicated phenomena of our district evidence frequent oscillations of 

 level, and repeated changes of land, freshwater, and marine conditions. During 

 the carboniferous era, this district had its hills and valleys, its rivers and lakes ; 

 but there were also extensive, low-lying plains, rank with vegetation, bordering on 

 the sea. These swamps were converted into lakes, and the submerged vegetation 

 was covered with sand and mud, in which were stems and branches of trees ; other 

 changes succeeded — the waters gradually became shallower, and at length a new 

 marshy surface appeared, supporting vegetation as luxuriant as before ; after the 

 lapse of ages, the scene is again changed — the vegetable accumulations have sunk — 

 the waters of the ocean have rolled over it, and eventually it is covered with lime 

 and mud beds, which are crowded with marine animals, that had lived and died on 

 the spot where they are now entombed. 



" The carboniferous deposits have a wide range in both hemispheres, from the 

 arctic regions down to the 33° of north latitude. Over the whole, the same general 

 conditions prevailed, for the same peculiar flora is found in every portion of it. 

 That flora was not varied, though extraordinarily luxuriant and enormous in the 

 aggregate. At present there are in Great Britain 1428 species of flowering plants 

 and ferns, but only 300 species have been found belonging to the carboniferous 

 era. The different proportion of ferns is also remarkable ; for while nearly one 

 half of the carboniferous flora are ferns, they constitute only about l-35th part of 

 the entire existing flora. Conditions such as are indicated by the carboniferous 

 flora are to be met with only in countries, especially in islands, bordering on the 

 tropics ; and it may, therefore, be inferred that the climate of the era was humid 

 and equable, and, if not warm, at least temperate. This conclusion is strengthened 



