SECTION VI. GEOLOGICAL PHENOMENA RESULTING FROM THE EARTH'S PROTOROTATION. CHAPTER XXII. The evidences adduced, and the points established in the foregoing chapter, briefly applied. Firstly. To explain the enigma of the presence of crystallization, arising from both aqueous and igneous fusion observable in the rocky crust of the Earth. Secondly. To account for the existence, in the same, of mineral veins and dykes of Granite, Porphyry, Trap, &c. &c. Geological evidences in confirmation of these two branches of enquiry. A few concluding observations. THE fusion of the injected, amorphous rocks, which everywhere so abound in fields of geological investigation, and the means employed to effect their fusion-as pre-supposed by what has been stated in the foregoing chapters-could scarcely have been better authenticated. The evidences adduced are perfectly conclusive; for, that which ought to have been the result of the application of fierce heat, under the circumstances presumed, having been premised, the experience of geologists, in their researches amongst the same rocky formations, has been adduced, and the two are found closely to coincide; while the wisdom of the method which was adopted by the Creator has been made most manifest. In contemplating the harmony which, by these two methods of investigation, is seen to prevail, we cannot fail to be impressed by the wisdom and goodness which are displayed, as well in the time as in the mode of their execution; and gratified, besides, that science has been the means of revealing these to us. For it appears evident by the two Theorems which have been alluded to,* that the fusion of calcareous rocks is greatly facilitated by pressure, and by exclusion from the air; these conditions serving to retain their gaseous components: and that the same object is likewise attained by their being subjected in great masses to the sudden application of heat; while their gases are bound up and rendered innocuous by union with lime, or by decomposition, and the oxygen set free by the action of plants. Therefore, had this universal and intense fusion of limestone taken place in atmospheric air, and after the formation of the vegetable kingdom, so much carbonic acid would have been evolved, that animal life dependant on pulmonic action could not have existed. But by opportunely choosing the time, and performing the whole in one grand operation, all these requisite conditions, being foreseen, were duly provided for! By the evolution of the heat beneath the primeval waters, and before the formation of the atmosphere and the vegetable kingdom, the otherwise noxious gases were rendered beneficent, and subservient to the future wants of man; the same provident forethought being ever present in all the works of the Creator. By this we are, likewise, supplied with a striking corroboration of the exactness of the epoch, assigned by the inspired historian, as that of the elevation of the continents and mountains of the earth, from its having taken place beneath the pressure of the ocean, and while as yet there was no atmosphere. The application of these conclusions may assist to unravel one of the greatest enigmas attending geological research. We allude to the evidences which exist in the rocky masses to lead to the undeniable conclusion, that crystallization, both by aqueous and igneous means, has been employed in their formation a fact which, to account for seemed to require, that recourse should be had to such probabilities as could scarcely be conceded. But now, we think, we can clearly perceive, that aqueous crystallization was employed to aid in forming these masses in a horizontal position before the earth was made to rotate; igneous crystallization, arising from fierce heat occasioned by friction, having been afterwards evolved to * 24th and 101st Theorems. complete their structure, when they were simultaneously raised from that recumbent posture by the first diurnal movement of our sphere; while it is obvious that as this latter crystalline structure is the effect of heat; and heat, in the instances alluded to, arose from friction; and these, in turn, were occasioned by the general movement, entre se of the mineral masses composing the crust of the globe, then the ultimate result-crystallization-would be at its maximum amongst the more elevated and more disturbed formations; those which travelled farthest from horizontality having, consequently, evolved most heat. These natural and unconstrained conclusions supersede the necessity of recurring to supposed sudden and capricious transitions from one description of crystallization to another; and while they relieve us from this, they reveal the cause of those phenomena which intrude themselves so strongly upon the notice of geologists in these departments of their research. What has now been said has also sufficiently proved, that violent movement did take place during the epoch referred to, amongst those masses of mineral matter which now constitute the rocky formations of the earth's surface; as shown by the local fusion, which was the immediate consequence; and that therefore, the foci of heat were in the centres of motion, that is, in the highest elevations. It must, also, be obvious that if these rocks, so circumstanced, were impelled by the centrifugal impetus with so much force as to elevate the superincumbent strata; veins, or branches of the fused material, should be found not only insinuating themselves into the crevices formed by the strata, where they were shook and distorted by the general commotion; but, likewise, that these streams of fused mineral should be discovered to have burst through and overcome every obstacle, when the superincumbent masses did not separate so as to permit them to pass. On referring to the facts which have been brought to light by the investigations of geologists, it is discovered, that rocky protrusions, called veins and dykes, of the description and character here anticipated, are frequently found intersecting the whole series of formations, from the primary to the surface inclusive. But let geology speak for itself. The twenty-ninth Theorem, and its accompanying evidences, state" That when a view is taken of any geological map, it is observed that the formations represented by it are intersected by veins of granite, porphyry, senite, trap, serpentine, greenstone, &c., and by dykes of similar material, especially of trap and basalt. That whatever may be the nature or position of the formations through which they pass, the general direction of the main trunks of these veins and dykes is perpendicular to the earth's surface, although their branches frequently diverge and weld the several formations together in a remarkable manner. And that overlying masses of the same materials are frequently found on the surface, as if they had overflown from the veins while in a state of fusion." "Within the primary granite," says Professor Buckland, "we find other forms of granitic matter, which appear to have been intruded in a state of fusion, not only into older fissures of the older granite, but frequently also into the primary stratified rocks in contact with it, and occasionally into strata of the transition and secondary series. These granitic injections were probably in many cases contemporaneous with the rocks they intersect; they usually assume the condition of veins, terminating upwards in small branches; and vary in dimensions from less than an inch to an indefinite width. The direction of these veins is very irregular; they sometimes traverse the primary strata at right angles to their planes of stratification, at other times they are protruded in a direction parallel to those planes, and assume the form of beds. "Closely allied to granitic veins, is a second series of irregularly injected rocks, composed of senite, porphyry, serpentine, and greenstone, which traverse the primary and transition formations, and the lower regions of the secondary strata; not only intersecting them in various directions, but often forming overlying masses in places where these veins have terminated by overflowings at the surface. The crystalline rocks of this series present so many modifications of their ingredients, that numerous varieties of senite, porphyry, and greenstone occur frequently in the products of the eruptions from a single vent. "A third series of igneous rocks, is that which has formed dykes, and masses of basalt and trap intruded into, and overlaying formations of all ages, from the earliest granites to the most recent tertiary strata. These basaltic rocks sometimes occur as beds, nearly parallel to the strata into which they are protruded, after the manner represented in the carboniferous limestone of our section. More frequently they overspread the surface-like expanded sheets of lava."* "The last circumstance," Dr. M'Culloch states, "in the geological character of granite, relates to its distribution in the form of veins, of which there are two distinct kinds. The first lie wholly within the rock, consisting of the same materials, under slight differences in the colour and magnitude of the parts, being also connected with similar variations, of a concretionary appearance without the veinous form. The next are much more interesting, and constitute the principal arguments respecting the posteriority of granite to the strata with which it is associated. These vary infinitely in their dimensions, extent of course, entanglement, and ramifications. At times, they are rather protuberances from the general mass than veins, while at others, they extend to great distances, insinuating themselves widely into the surrounding strata, above all, in gneiss, in which rock also they especially abound. Thus, also, their thickness varies, from many yards even to the minuteness of a thread, being simple or ramifying; and often also presenting the most intricate reticulations. In composition, the larger veins at least, sometimes, resemble the purest mass, while, in the smaller, the structure often becomes minute, as if proportioned to the size of the vein. But more commonly, the materials are crystallized on a much larger scale, producing the well-known specimens of felspar and mica, as, in these veins also, the accidental minerals enumerated in the classification are chiefly found. Yet the size of the ingredients does not bear a proportion to that of the vein; the larger crystallizations as often occurring in the small as in the large ones."† "Thus far," says M. de la Beche, "we have only seen granite rising through and covering other rocks in considerable masses, but we have also evidence in granite veins, that the matter of the rock was in such a state of igneous fusion, as to penetrate into thin clefts opened in stratified and older rocks, by some violence, such as probably resulted from the upburst of igneous matter accompanied by elastic vapours. . . . "Glen Tilt, which produced such delight to Hutton when viewed by him for the first time, presents excellent examples of the intru * Bridgewater Treatise, vol. ii. pp. 4—6. + Geology, by Dr. M'Culloch, vol. ii. pp. 95, 96. |