334 PROCEEDINGS OF SOCIETIES. 



epochs it teemed with life. Some chemical condition unfavourable 

 to their preservation must have operated in the earthy matter which 

 enveloped them : — a strange condition indeed which permitted solid 

 matter to be dissipated and not an atom of the soft and succulent 

 vegetable to perish. The carbonate of lime of the shell — the phos- 

 phate of the skeleton — and even the si lex of cercalia and grasses 

 alike yielded to the solvent — the imperishable carbon alone sur- 

 vived. So with the fruits, the shelly envelope has vanished and the 

 destructible portion remains. It may be, as has been imagined, that 

 the succulent plants imbibed the conservative principle from the at- 

 mosphere, and there are many circumstances which favor the hypo- 

 thesis that it was the office of the vegetation of that period to ab- 

 stract from the atmosphere the excess of carbon, and thus whilst the 

 ait was being made respirable for man and the animal races who 

 were in aftertimcs to inhabit the earth, inexhaustible supplies of 

 that invaluable treasure, coal, were laid up for our use in the latter 

 ages of the world. 



These, hovever, it is evident, are secrets of Nature's Laboratory 

 which may never be revealed to us. Science may attempt to imi- 

 tate, human ingenuity speculate in vain. 



There is another circumstance to which I must briefly refer, viz. ; 

 the i-emarkable coincidence observable between the geological distri- 

 bution of fossil plants and the geographical range of the existing 

 vegetation — a result perhaps the most singular that has attended 

 the study of this subject. It may be thus popularly illustrated, 

 without going into details : — Sujipose a traveller to journey from 

 the equator to the polar regions of the earth, he might thus charac- 

 terize the different scenes of vegetation which distant parallels of 

 latitude, or, better, the isothermal zones would present. He is now 

 under the tropics, surrounded by dense and interminable forests of 

 gigantic evergreens and ever-blooming trees of a hundred species of 

 Palm, Bamboos, Tree-ferns, and Bananas, beneath whose refresh- 

 ing shade a thousand Cadi and Euphorbise bristle the earth, aroma- 

 tic shrubs jrive out clouds of perfume, and high in air hangs the epi- 

 phitic Orchis, whilst Cable Canes, hundreds of feet in length, trail 

 along the ground. But he leaves the torrid zone, and grassy meads 

 succeed to tropical junj,'lcs ; the forests of columnar branchless trees 

 with leafy crowns peering almost to the clouds, and forming so re- 

 markable a feature in the landscape of intertropical climes, diminish 

 into shrubs and gradually disappear, whilst the picturesque forms 

 of the Oak, the Elm, the Chesnut and the Pine — the forest-trees of 

 Europe — now meet his eye. Corn and wine, instead of the bread- 

 fruit and olive, sup}>ly his wants; and where the soil is saturated 

 with humidity, i)istead of Bamboos and Canes, Grasses, Sedges, and 

 Reeds prevail. The Tree-fern has dwindled into an insignificant 

 herb, and other trees, whose foliage yields so delicious a shade be- 

 neath a tropical sun, by degrees become dwarfish shrubs and eventu- 

 ally puny herbs. The Orchis leaves its abode in the air, and clings 

 to the soil for support. In higher latitudes the scene undergoes a 



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