Objections to Geology.

I HAVE felt it desirable to dwell the more particularly on the strictly inductive character of geology, not only on general grounds, but more especially because much pains and some ingenuity have been employed to disparage and even deny the evidence of this science*. To some such objections we have already referred; and the rest are not more rational or more consistent. When refuted on other grounds, their upholders take refuge in the convenient maxim, that after all, geology is but in its infancy, and as many theories once adopted have now been rejected, so those now in vogue may be in their turn exploded: or again, they contend that the utmost extent of our researches has not penetrated beyond the mere crust of the earth, how then can we pretend to draw such general conclusions?

If the science be in its infancy, we can only say that it has displayed such vigour as already to have grappled with and overcome the most formidable attacks. False theories have indeed been exploded; but the order of advance has been regular and systematic; the early cosmogonical speculations have indeed been discarded, for the simple reason that they were not founded on induction, but on some foreign principle or authority, and therefore had no substantial or enduring consistency. A remnant of the same spirit, however, continued

* See Note B.

to linger about the schools of geology, and displayed itself in later times in the diluvial hypothesis, and others of the same nature. These, in their various modifications, have since given way, and for the very same reason, because their foundation was defective; it was based on some other authority than that of simple induction. So the belief in vast and sudden revolutions in the state of the entire globe has been discarded; the inductive principle is extending its triumphs, and if all the phenomena presented by the observed state of the earth's surface have not been actually explained by the action of known causes, yet many have been which were before not perceived to be capable of such explanation; and it has become generally admitted that this is the only sound method to be pursued in the endeavour to throw any real light upon them.

In this way, and in this steady course of advance from the hypothetical to the matter-of-fact, may geological theories come to be successively modified, but in no other. Those who make this a topic of objection must, therefore, prepare themselves to expect, in the changes they may anticipate, nothing favourable to any preconceived hypotheses, but every thing tending still more and more to take a direction entirely opposed to those favourite schemes of cosmogony which have usually prompted these and the like objections.

And if, as the objectors urge, we have penetrated as yet only a thin film, as it were, of the mere out

ward crust of the earth, how completely does the obvious inference recoil on themselves! If by going only to this trifling extent, we have succeeded in obtaining such a mass of evidence, and substantiating such vast and overpowering conclusions, what may not result when our inquiries shall be able to penetrate still deeper?

The introduction of imaginary systems of cosmogony into geology, is but an exemplification of the same fallacious principles of speculation, by which every branch of physical inquiry has, in its turn, been impeded and perverted. It was in the same spirit that Kepler believed the globe to be a living animal: that Tycho Brahe feigned the sun with his attendant planets to revolve round the earth: and that the equilibrium of the mercury in the barometer, was ascribed by Linus to a suspension by invisible threads.

False Philosophy from neglect of Analogy.

THE same want of inductive principles, the same spirit of gratuitous theorizing, which prevailed in the disputations of the schoolmen, characterized in no less degree the speculations of Descartes and his followers, which in a later age took their place. The main error which pervaded the whole system of that eminent philosopher, was the adoption of a metaphysical basis, on which to rear the edifice of physical truth. Or, in a word, the introduction of

some other guiding authority than simply that of natural analogies, suggested and supported by the habitual recurrence to the sole test and standard of experimental evidence.

From the influence of the same cause, even in comparatively modern times, it required a long struggle to divest chemistry of that chimerical theory of combustion, whose advocates imagined "phlogiston," a sort of metaphysical something, they knew not what, which conferred on bodies the property of being combustible, and was abstracted during the process.

In this recurrence to principles alien from those of induction, we find the radical defect common to the ancient as well as the modern scholastic theories. This was the fundamental mistake which vitiated alike the system of the peripatetics and the Hutchinsonians; which upheld the crystalline spheres and the ætherial vortices-the starry influences and the diluvial cataclysms; the cosmogonists' chaos and the philosophers' stone.

It was to guard against such erroneous modes of speculation, that Bacon, in his Novum Organon, dwelt so earnestly on the principal sources of error which had arisen, or were likely to arise, in philosophical speculation, from the neglect of those just rules and principles. The several chief causes of mistake, which lead men into unsubstantial and delusive theories, classified under their respective heads, are what he designates in his somewhat

fanciful, but abundantly expressive, language, by the name of "Idola," the false divinities which the mind is apt to raise as the objects of its adoration, when it ought to be engaged in the sole worship of truth.

It is far from my design here to enter into any discussion of those sources of false philosophy. The excellence of Bacon's suggestions, as well as their importance, not merely for the guidance of the philosophical inquirers of his day, but as involving the correction of mistaken ideas, likely to be perpetually recurring, will be recognised by all who have examined his immortal work: and it will be the less necessary for me to insist on them here, since I have elsewhere placed them in a light accessible to the general reader*.

I will merely remark here, that the class termed "Idola theatri," seems to include the chief source of error to which I am here more especially referring : the adoption of artificial systems, founded on an assumption either of fallacious physical principles, or of any whatsoever not physical: the former being essentially false, the latter, however good in their own way, utterly inapplicable to the purposes of physical inquiry.

* See "History of Physical Science," Cabinet Cyclopædia, P. 198,

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