Volume 2

Principles of geology, being an attempt to explain the former changes of the earth's surface, by reference to causes now in operation / By Charles Lyell, esq.

  • Lyell, Charles, Sir, 1797-1875.
Date:
1830-1833
Catalogue details

Licence: Public Domain Mark

Credit: Principles of geology, being an attempt to explain the former changes of the earth's surface, by reference to causes now in operation / By Charles Lyell, esq. Source: Wellcome Collection.

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    tuating and temporary conditions in the state of the animate and inanimate world ? Fourthly, whether there be proofs of the successive extermination of species in the ordinary course of nature, and whether there be any reason for conjecturing that new animals and plants are created from time to time, to supply their place ? WHETHER SPECIES HAVE A REAL EXISTENCE IN NATURE. Importance of this question in Geology.—Before we can ad¬ vance a step in our proposed inquiry, we must be able to define precisely the meaning which we attach to the term species. This is even more necessary in geology than in the ordinary studies of the naturalist ; for they who deny that such a thing as a species exists, concede nevertheless that a botanist or zoologist may reason as if the specific character were constant, because they confine their observations to a brief period of time. Just as the geographer, in constructing his maps from century to century, may proceed as if the apparent places of the fixed stars remained absolutely the same, and as if no alteration was brought about by the precession of the equi¬ noxes, so it is said in the organic world, the stability of a spe¬ cies may be taken as absolute, if we do not extend our views beyond the narrow period of human history ; but let a suffi¬ cient number of centuries elapse, to allow of important revolu¬ tions in climate, physical geography, and other circumstances, and the characters, say they, of the descendants of common parents may deviate indefinitely from their original type. Now, if these doctrines be tenable, we are at once presented with a principle of incessant change in the organic world, and no degree of dissimilarity in the plants and animals which may formerly have existed, and are found fossil, would entitle us to conclude that they may not have been the prototypes and pro¬ genitors of the species now living. Accordingly M. Geoffroy St. Hilaire has declared his opinion, that there has been an uninterrupted succession in the animal kingdom effected by means of generation, from the earliest ages of the world