328 



FARMERS' REGISTER. 



[No. 6 



Now, a proportion, even very feeble, ofcarbon- 

 ic nc.ul, in the atmospliere, is generally an obsta- 

 cle to the existence of animals, and particularly of 

 the most perfect classes of them, as mammifers, 

 and birds ; while, on the contrary, this proportion 

 is highly favorable to the growth of vegetables: 

 and if we admit that there existed a proportion 

 very much greater of this gas in the primitive at- 

 mosphere of our globe than the present atmos- 

 phere is Ibund to contain, we may consider this 

 one of the principal causes of the powerful vege- 

 tation of these ancient epochs. 



This collection of vegetables, so simple, so uni- 

 form, and which would consequently have been 

 so little fitted to furnish suitable aliment for ani- 

 mals of diversified structure, such as those exist- 

 ing at the present day, in purilying the aimo- 

 ephere of the carbonic acid which it then contain- 

 ed in excess, would have prepared the conditions 

 necessary to a creation more varied : and il' we 

 still wish to indulge that sentiment of pride which 

 has caused man to assume that all in nature has 

 been created exclusively for him, we may suppose 

 tliis primitive, vegetable creation, which preceded, 

 by so many centuries, the appearance of man 

 upon the earth, was, in the economy of nature, 

 designed to prepare the atmospheric conditions ne- 

 cessary to his existence, and at the same time to 

 accunaulate those immense masses of combusti- 

 bles which his industry was in future time to ap- 

 ply to his necessities. 



But, independently of this difference in the na- 

 ture of the atmosphere, which the formation of 

 these vast depots of fossil carbon renders extreme- 

 ly probable, may not the nature of the vegetables 

 themselves, that have produced them, furnish 

 some data upon the other physical conditions to 

 which the surlttce of the earth was subjected du- 

 ring this period 7 The operations of nature now 

 going on in different regions of the globe, may 

 throw some light upon this question. 



The study of the geographical distribution oi 

 those plants appertaining to the same families 

 which alone composed the vegetation of the coal 

 period, may, indeed, indicate to us the climacte- 

 rick conditions and consequently the physical 

 causes which lavored the increase of stature as 

 well as the great frequency of these vegetables ; 

 and we may conclude fiom these, with much pro- 

 bability, that the same causes determined their 

 preponderance at that epoch. 



We see Ibr example, that the ferns, equiseta, 

 and lycopodijB attain a more lofty stature in pro- 

 portion as their geographical position approaches 

 the equator. Thus it is only in the hottest re- 

 gions of the globe, that we find those arborescent 

 ferns which combine with the towering and ma- 

 jestick mien of the palms, the elegant foliage of 

 the ordinary ferns, and of which we have indicat- 

 ed the existence in the coal formations. In these 

 same regions the equiseta and lycopodia? attain to 

 a stature double or triple that which the largest of 

 these species present in temperate climates. A 

 second condition appears to have a still more 

 marked influence upon their preponderance, in re- 

 ference to the vegetables of other families, name- 

 ly, humidity and uniformity of climate ; conditions 

 which are united in the highest perfection, in the 

 small islands situated far distant from continents. 



In such islands, indeed, the extent of the sur- 

 rounding oceans fi.xes a temperature with but 



slight variations, and coupled with perpetual hu- 

 midity ; circumstances which appear to favor, in 

 a remarkable manner, the development and the 

 variety of specifick forms among the ferns and the 

 analogous plants; while, on the contrary, under 

 the influence of the same conditions, the pheno- 

 gamous plants are little varied, and are i'ar less 

 numerous. From these causes it results, that 

 while on the extensive continents of the earth the 

 vascular cryptogamick plants, such as the ferns, 

 lycopodite, equiseta, &c. often form scarcely one- 

 fiftieth of the total number of vegetables, yet in 

 the small islands of the equatorial regions, these 

 same plants constitute almost half, and in some 

 cases, even two-thirds of all the vegetables which 

 inhabit them. 



The archipelagos, situated between the tro- 

 picks, such as the islands of the great Pacifick 

 ocean, or the Antilles, are, then, the points of the 

 globe which at the present time present vegeta- 

 tion the most analogous to that which existed 

 upon the earth when the vegetable kingdom 

 commenced, for the first time, to develop itself 

 thereon. 



Detailed examination of the vegetables which 

 accompany the coal cannot fail, therefore, to in- 

 duce the inference that at this remote epoch the 

 surface of the earth, in the countries where are 

 found those vast depots of fossil carbon with which 

 we are most familiar, namely, in Europe and 

 North America, ofi'ered the same climacterick 

 conditions which now exist in the archipelagos of 

 the equinoctial regions ; and probably a geogra- 

 phical configuration little difl^erent. 



When we consider the number and thickness 

 of the layers which constitute most of the coal 

 formations, and examine the changes that, from 

 first to last, have taken place in the specifick forms 

 of those vegetables of which they have been con- 

 stituted, we cannot fail to see that this stupendous 

 primitive vegetation, during a long interval, must 

 have covered with its dense forests all parts o( 

 the globe which were at that period elevated 

 above the sea ; lor all these present themselves 

 with the same characteristicks in Europe and 

 America ; and equinoctial Asia, as well as New 

 Holland, seem therefore to have participated, in 

 this general uniformity of the structure of vegeta- 

 bles. 



Nevertheless, this primitive vegetable existence 

 promptly disappeared, to give place to a new cre- 

 ation, composed oC beings of an organization less 

 extraordinary than the preceding, but almost 

 equally diflerent from such as flourish at the pre- 

 sent dajf. 



To what cause can we attribute the destruction 

 of all the plants which characterize this remarka- 

 ble vegetation. 



Is it due to some violent revolution of the globe? 

 Did it arise from the gradual change of the phy- 

 sical conditions necessary to their existence; a 

 change in part arising from the presence of these 

 vegembles themselves? These questions cannot 

 be resolved in the present state of our knowledge 

 upon the subject. 



Certain it is, however, that the deposition of 

 the last layers of the coal formation was followed 

 by the destruction of all the species which consti- 

 tuted this primitive vegetation, and particularly of 

 those gigantic trees of peculiar structure, as the 

 lycopodiacetc, the ferns and the equiseta of gi- 



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