We readily admit that the time has not arrived, and may perhaps be still far distant, when the experimental philosopher may safely employ final causes as the leading clue in his inquiries. In the history of ancient, and the early periods of modern physics, final causes were often assigned, before the proximate or operative causes had been explained, or perhaps examined. This inversion of inductive logic, need hardly be apprehended from any experimentalist of reputation in the present day. In such circumstances, therefore, the temperate use of final causes may be encouraged, first as serving to arrange several inductions under a general head, but especially as displaying the concerted harmonies of Providence. The outcry against them is one of the countersigns of the sceptical school. Physical lessons for youth and the people should be selected with care. That the system of nature has been, and may be exhibited, in so distorted a form, as to impress improper images on the common mind, will hardly be denied by the most zealous partisan of the knowing faculties. On this delicate topic, I gladly avail myself of the following acute remarks from a work, distinguished for the liberality of its views. "In sober truth, doubts are excited in minds, that had never heard of doubts, or suspected their existence. Tremaine gives the means of doubting, but he does not give the antidote. His counter arguments will not confer the power of reasoning, the feelings side invariably with the devil, and the result is consequently obvious. It is not by the dry statement of opposing arguments, that the dialogist can carry the victory which he feels he possesses in himself; the affections or the prejudices, human depravity or human pride, takes a part; the bias is on the wrong side, and he who does not like to be convinced, naturally sides with the antagonist."* • Westminster Review, Vol. IV. p. 301. BRYDONE'S LAVA STORY. xlv. This is a sufficiently humiliating account of the natural propensities of the human heart. Discretion should therefore be exercised in preparing mental food for the people.. Only sound articles should be served up, and such equivocal speculations be witheld, as may readily ferment into moral poison. In the course of my own public experience during a quarter of a century, I have often observed the avidity with which every phenomenon apparently adverse to natural or revealed religion is seized, and the reluctance with which it is renounced by the will, long after the fallacy has been made manifest to the understanding. Thus, for example, I have met with individuals of considerable pretensions to candour and sagacity, who having devoured with greedy eyes, the story told by Brydone, in his Sicilian Tour, about the Canon Ricupero, conceive that it justifies them in reviling the chronology and character of Moses. The Canon, though a weak enough theorist, was a man of undoubted piety, and had certainly no desire to call any Bible truth in question. Dolomieu, who knew him, censures severely the Scottish traveller for his ungenerous return to the Canon's hospitality, in unhandsomely exposing him to ridicule, and but for his excellent private character, to the castigation of the church. Ricupero is said to have fancied that a bed of lava required 2000 years to gain a coating of soil, by the decomposition of its surface. Having observed in a pit in the neighbourhood of Ætna, 7 lava beds lying over one another, with a stratum of rich earth between each, he was said to infer that the mountain was 14,000 years old. His bishop is also reported to have counselled him not to make his mountain older than Moses had made the earth; a most philosophical advice, as we shall presently see. The facts exhibited by Etna are so directly hostile to any such conclusions, that we can hardly suppose the Canon ever to have formed them; and are led to suppose the story a mere jest, got up in contempt of the Canon's feelings, to please the dissolute society, in which Brydone is known to have lived for some time. Let us see what a geologist says, in treating of Etna, who probably never heard of the Scotchman or his travels. "The lava of 1157 is covered with 12 inches of vegetable earth proceeding from its own decomposition; that of 1329 is covered with 8 inches. On the other hand, several of the lavas of Auvergne have maintained an entire surface, all over blistered, and bristling with asperities, whose edges and angles are still sharp and well preserved. We might even imagine these lava streams to have just flowed from the bowels of the earth, and that they had hardly had time to cool. It is, however, probable that these lavas have lain on the soil of Auvergne for 3000 years, exposed to the action of the elements. Two thousand years have elapsed since Cæsar encamped upon them; and even in his day tradition could tell him nothing about their origin. The fertility of the lands on Etna, however, is a subject of admiration to all who visit the mountain.”* Here we see, in the first place, that no inference whatever can be made as to the age of a lava, from the state of its surface. The tendency to decompose differs in every specimen. We see, in the second place, that in 500 years a good vegetable mould may be formed, which multiplied by 7, carries us back to a period only 600 years after the deluge. Prior to the appearance of Brydone's book, Sir William Hamilton had shown that over Herculaneum in less than 1700 years, "the matter of 6 eruptions has taken its course over that which lies immediately above the town, and was the cause of its destruction. These strata are either of lava or burnt matter with veins of good soil betwixt them.+ Here 243 years are enough for decomposition, instead of Brydone's 2000. • D'Aubuisson Geognosie, Tom. II. pp. 592, 593. NEW ERA OF PRACTICAL GEOLOGY. xlvii But the most singular evidence remains, about this castle of scepticism. In Dr. Daubeny's interesting sketch of the geology of Sicily, drawn up after an extensive tour lately made in the island, we have the following description of the beds of lava in the famous pit, at Aci Reale, on which Ricupero was made to speculate. "At all events Brydone has been grossly deceived in imagining, that the seven beds of lava seen lying, one above another, near the spot, have been sufficiently decomposed into vegetable mould; the substance which really intervenes between the beds being nothing more than a sort of ferruginous tuff, just similar to what would be produced by a shower of volcanic ashes, such as usually precedes or follows an eruption of lava, mixed up with mud or consolidated by rain. Of course, his inference with respect to the antiquity of the globe, falls to the ground, as being founded on the fact of the decomposition of so many beds of lava, which turns out to be altogether a mistake."* Geologists have begun, of late years, to survey the structure of the earth in more minute and patient detail, than their dashing predecessors; to compare, by map and section, its most interesting provinces; to contemplate individual facts directly, and not through the dark and distorting medium of a master's cosmogony; and to examine, with zoological skill, the organic inscriptions of its different In thus studying to decipher the volume of its shelly records, they have explored many mysteries, inscrutable by Werner, Hutton, and the early fanatics of their schools, to whom the very alphabet of the language was unknown. In this new field of knowledge, the English nation stands pre-eminent; against no mean rivalry, however, of the naturalists of France. Emulation has here produced the happiest effects; for while the mineral super strata. Edinburgh Philosophical Journal, Vol. XIII. p. 266. positions of England have received admirable illustration, from the sagacity of Smith, Greenough, Macculloch, Conybeare, Phillips, Buckland, De la Beche, Webster, Winch, and several other members of the London Society, Brogniart and Von Buch have revealed many wonders in French, Swiss, and Italian geology, and the two Cuviers, Blainville, Lamarcke, and Defranee, have thrown surprising light on the zoology of fossils. By directing his profound knowledge of comparative anatomy, to antediluvian osteology, Sir Everard Home has gathered fresh laurels; nor have the German and Italian mineralogists been forgetful of their fame in this difficult career. The joint labours of all these philosophers, have been embodied by a master's hand, along with his own unrivalled studies in the Ossemens Fossiles of Baron Cuvier; a magnificent production of which, it is difficult to say, whether the science, eloquence, or candour, be most worthy of admiration. By such conspiring researches, an interesting gradation has been traced in the species of organic exuviæ distributed throughout the secondary strata, in their order of superposition. Each successive mineral bed is the sepulchre of a peculiar colony of shellfish. These relics of life have thus acquired singular importance. They furnish stereotype pages, so to speak, by which the corresponding or equivalent geological formations may be read and recognised in every terrestrial zone, however interrupted the mineral planes may be, by ravines, mountains, or seas. Shell-limestone constitutes the main body of secondary formations; which indeed may be regarded all together as only one enormous calcareous stratum, forming, with a few interruptions, the external envelope of the solid mass of the globe, and alternating occasionally with ranges of gypsum, marl, sandstone, and clay.* That conchiferous strata are as common in remote regions, as at home, the general reader may learn from the following account of the structure of rocks in places, with whose names, at least, he must be familiar. |