578 THE UNIVERSE. 



During this period the whole surface of the globe was 

 covered with strange and dense forests, where proudly 

 reigned a host of plants, the representatives of Avhich at 

 the present day play but a very humble part. Here were 

 palms and baml^oos, there gigantic Lycopodia, which, now 

 humble creeping herljaceous plants, at that time bore 

 straight stems towering to a height of eighty to a hundred 

 feet. Then came the Lepidodendra, the stem of which 

 reminds one of a re2)tile's scaly cuirass. Lastly came trees 



mi 



nes take their origin, an attempt has been made to estimate their duration and 

 antiquity. M. Chevandier, computing the product of two plantations of beeches 

 for a given period of years, found that the carbon of our contemporary forests 

 would in a hundred years only form on a hectare (or, in round numbers, t^vo 

 acres one rood) a layer of coal seven lines in thickness. This calculation sufficed, 

 in the eyes of some statisticians rather ingenious than rigorously scientific in 

 their statements, to fix the duration of the forests, the deposits from which now 

 form our coal. They have come to the conclusion that these coal-beds represent 

 the concentrated products of a vegetation which lasted 672,788 years. Bischoff 

 devoted himself to other calculations: the learned German physiologist wanted 

 to ascertain how many years separate us from the carboniferous period. Accord- 

 ing to him we must date it back 9,000,000 years from our era. But it is evident 

 tliat these calculations, like the preceding ones, are only hazardous investigations 

 without the least scientific exactitude. 



[As regards the great cpiestion of exhaustion of coal, M. Leonard Lemoran has 

 pointed out that, so far from our being able to calculate with any certainty at 

 what iieri(jd the coal-fields of England will be exhausted, we are not yet in pos- 

 session of tlie first elements of such a problem ; that the area occupied by coal 

 within the carboniferous dejjosits liasnever yet been determined with accuracy; but 

 he concludes, that at the present rate of consumption, the coal in the South Wales 

 basin will last for 2000 years, and that probably we shall not materially exceed 

 our present rate of consumption, as the increase of price which is going on will be 

 a natural check upon it ; that our coal-seams extend under the Permian and New 

 Red Sandstone rocks ; that coal-seams exist at much greater depths than any now 

 worked, and that they may very possibly be worked at a gi-eater depth than was 

 supposed (4000 feet). This is a more encouraging view than that taken by Sir 

 William Armstrong, who limits our supply to 212 years; or that of Mr. Edward 

 Hull, of the Geological Survey, who extends the limit to a little upwards of 300 

 years. — Popular Science Review, vol. v. p. 290. 



Enormous masses have recently been discovered in Russia. One coal-bed, in 

 the district of which Moscow is the centre, covers an area of 120,000 square 

 miles! and is therefore almost as large as the entire bituminous coal area of the 

 United States.— Tr.] 



