PUOCEEDINGS OF SOCIETIES. 335 



slill greater change : not only is the luxuriant growth of the warm- 

 er regions no longer visible, but the number of species of ])lants is 

 greatly diminished, until, arrived at the circum-polar regions, the 

 only representatives of the glorious forests of the tropics are the 

 Mosses which vegetate in the swamps, the Lichen which clings to 

 the icy rocks, or the Protococci which discolours the eternal snows ! 



In the fossil world, the latter scenes have no counterpart, for Ge- 

 ology knows no icy period : but in every other particular the geolo- 

 gist recognizes an epitome of the phenomena which we have des- 

 cribed. Beginning with the productions of the temperate climate 

 of Europe, of our own country and times, we trace in succession 

 their gradual disappearance with the animals which have browsed 

 upon the pastures or roamed in the forests. We mark the first ad- 

 vent of the Palm-tree in these latitudes, or rather the last, for we 

 are going up the stream of time ; the herbaceous Ferns give place 

 to the more noble tree, and ere we leave the tertiary rocks the Palm- 

 tree is predominant. In the secondary rocks some new forms meet 

 the eye : the Cycas connects the Palm with the Pine, and the Cac- 

 tus tribes abound — here, indeed we may repose in imagination be- 

 neath umbrageous Palm-groves and Bananas, or grope our way 

 through tropical jungles until we are lost in the dense forests of 

 Sigillaria and Lepedodendra, or swamped among the gigantic Equi- 

 seta of the marshes of our coal-formation — the lankness and exces- 

 sive luxuriance of whose vegetation distances all analogy drawn 

 from the present productive powers of the earth ! 



And it is not through the medium of the imagination alone that 

 this remarkable coincidence may be made palpable to the under- 

 standing. A numerical estimate of the relative proportions of pre- 

 vailing species of plants at different geological epochs, compared 

 with a similar computation of the relative number of species exist- 

 ing under similar circumstances (the same conditions of temperature 

 and humidity being assumed), gives a result which approximates as 

 nearly to the assumed hypothesis as can well be hoped for in the 

 limited state of our knowledge. In reference, however, to this, it 

 must not be forgotten that 50,000 living species of plants are recog- 

 nized by botanists, whilst only 500 fossil species are at present 

 known to geologists. 



In contemplating the wonderful phenomena with which the sub- 

 ject and specimens before us are connected, it is hardly possible to 

 resist the temptation to speculate upon the cause and the object of 

 these apparent vagaries of Nature : for strange indeed — " stranger 

 than fiction" — are the mighty secrets inscribed in her portentous 

 volume. Perhaps ail speculations as to the means employed in the 

 production of these phenomena, may be vain ; but the end accom- 

 pli.shcd is clear — so clear that it cannot be mistaken. Although 

 these Palm-fruits grew when there was none to eat — although the 

 cartli was adorned with beauty when there was no eye to admire, 

 and waste and desolation "joint empire ruled" through many an 

 age whilst " Chaos umpire sat" — has not a great and noble end 



