garnet, were produced by the "capricious play of the forces of chemical affinity."

The theory of gneiss is, however, much more unquestionably original. We must imagine, what in fact has been proved long ago in the first part of the work, a general intumescence of an intensely heated bed of granite, forming the original surface of the globe, succeeded by a period in which the predominance was acquired by the repressive force, occasioned by the condensation of the waters on its surface, and the deposition of sedimental strata forming the transition series. This "simply, at once," explains the lamellar structure of the gneiss formation. "And this structure may have been subsequently increased by the friction of the different laminæ against one another, as they were urged forwards in the direction of their plane surfaces towards the orifice of protrusion, along with the expanding granite beneath; the laminae being elongated, and the crystals forced to arrange themselves in the direction of the movement."

Hence the author proceeds to give what he calls a "conjectural rough sketch of the theory of the globe," which, with the exception of an appendix, terminates the present volume. We were not

wrong, then, in considering all that we have already quoted as matter utterly new, since he concludes, that however imperfect this theory may be, it is deduced from the views which he has laid down, and is "more accordant with the general and constant processes of nature than any other which the spirit of geological inquiry has yet started."

The mass of the globe, or at least its external zone to a considerable depth, was originally of a granitic composition with a very large grain.

On reaching its actual orbit, or before," it enjoyed a great diminution" of the pressure which had previously crystallized, or preserved it in a state of crystallization, at an intense temperature, perhaps as an integrant part of the sun.

Part of its atmosphere was lost in its passage from the sun, on the principle of a comet's tail; and the remainder formed the present atmosphere and the ocean, or the main reservoir of superficial waters.

The rotatory motion and the liquefaction of the surface produced the oblate form. And as the "process of expansion proceeded in depth," the original granite beds were liquefied; "the crystals being merged in the elastic vehicle produced by the vaporization of the water contained between the laminæ." And as the superior pressure forced it out, a quantity of aqueous vapour was produced on the surface of the globe, while its expansion lowering its temperature, it fell back again and produced water. Thus there were alternations, and consequently rain, and tor

rents, and many other things; and the waters of the ocean dissolved silex, and such other minerals as water under such circumstances could hold in solution. And then the disintegrated crystals that were suspended subsided; the felspar and quartz first, and afterwards the mica, as being more buoyant, and the pressure produced a parallelism gradually increasing, and thus were formed the gneiss beds.

A period at length arrived when the force of expansion was checked by the gravitating column, and thus it was stopped by this pressure" from progressing further inwardly." The lowest stratum was granite disaggregated, the next was granite disintegrated, reconsolidating into granite, the third became gneiss, and the fourth, zone, consisting of turbid and heated water, containing the other earths and minerals, formed mica and slate, carbonate of lime, and so on. The fifth stratum was aëriform, and formed the atmosphere.

And then as the evaporation of the ocean went on, more precipitations took place, and there were formed the transition formations and beneath this crust a new process was commenced. The outer zones of crystalline matter were refrigerated, and abstracted caloric from the nucleus; and by some other operations, which, we grieve to say, we cannot abridge, the process of consolidation" progressed downwards" with the increase of the expansive force in the lower strata, and the upper zone of crystalline matter which had intumesced was re-solidified, and the gneiss formation once more was the result. And beneath this, the granite was again solidified and returned again to its former condition; but the increasing expansive force overcame the resistance, and produced fissures, and thus the inferior crystalline zones came out of them in a "solid or nearly solid state," together with the intumescent granite, and extravasations in the form of lavas.

And the reason why the foliated rocks protruded so easily, was their peculiar structure, which allowed them to slide, while the crystals also were elongated in the direction of the motion, as happened in the "pearlstones" of the trachytic formation. And the rapid expansion of the crystalline rock in the fissures while the water was boiling, ground the crystals into powder, and produced" porphyries or serpentine;" while if the "particles were comminuted to an extreme degree by the friction attendant on the intumescence," they may have "effected entirely new combinations," and so produced diallage rock, hornblende rock, &c. And when the heat was not sufficiently great to boil the water, the aqueous vapour exuded through the walls, bringing with it silex in solution, together with other mineral and metallic matters sublimed from the lower part of the fissure.

Then all this commotion and breaking up produced the waves

as before, which broke up and triturated the projecting angles, and these were again deposited by subsidence. And then the ocean became peopled; and as portions of the strata had been elevated above the waters, vegetables were produced, and their fragments becoming carbonized, were washed into the sea, and became entangled among the subsiding strata, forming coal-beds. Subsequently, the temperature diminished, and the present creation appeared.

The final conclusion (since we fear that we are exceeding our bounds,) is, that the "grand mineral masses of every age, composing the known crust of the globe," are attributable to three primary causes: first, solution of certain minerals in water; second, suspension of fragments of various kinds and sizes; and third, the elevation of crystallized matter by intumescence or expansion, in a solid or fluid state.

And these causes, being perfectly original and new, “have an immense advantage over most, perhaps over all, of the hypotheses that have as yet been brought forward to explain the same appearances, and which speaks volumes in their favour: and this is, that they are still in operation-with diminished energy, it is true, but this is the necessary result of their nature."

The author concludes by remarking, that other geologists have erred by considering rather what might be than what is; that the laws of nature are invariable; that other geological theories have chiefly been dictated by a love of the marvellous, as the dark ages had recourse to supernatural causes; that this "wonder-working spirit" had inspired most of the geologists who have hitherto published theories to account for the mineral appearances of our planet; and that though the theory of the globe which he has himself proposed will require "much ulterior developement," "its truth will be established on the soundest possible basis;" because it proceeds by the application of those modes of operation, which nature still employs, and on that law on which all our knowledge rests, on every subject whatsoever," namely, that similar results always are, have been, and will be produced by similar preceding circumstances.

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ART. XIII. MISCELLANEOUS INTELLIGENCE.

1. MECHANICAL SCIENCE.

1. Effects of an Anti-Attrition Preparation.-A Munich journal reports the following results relative to the advantage obtained by employing a mixture of hog's-lard and plumbago for the diminu tion of friction in machines. The composition consisted of ten and a half parts of pure hog's-lard, fused with two parts of finely pulverized and sifted plumbago. The lard is first to be melted over a moderate fire, then a handful of the plumbago thrown in, and the materials stirred with a wooden spoon until the mixture is perfect; the rest of the plumbago is then to be added, and again stirred till the substance is of uniform composition; the vessel is then to be removed from the fire, the motion being continued until the mixture is quite cold.

This composition is to be applied to pivots, the teeth of wheels, &c., in its cold state by means of a brush, and is seldom required oftener than once in twenty-four hours. It was found that the machines employed in certain iron works, cost, in oil, tallow, and tar, as much per week as six florins twenty-nine kreutzers; but, upon replacing these substances by the composition described above, the expense was diminished to one florin thirtyeight kreutzers for the same time, 5 lbs. being required for the week's service. Economy to this extent is not to be neglected in manufactories where many machines are in use.-Ann. des Mines, xi. 79.

2. Strength of Leaden Pipes.-Experiments upon this subject have been made at Edinburgh by Mr. Jardine at the Water Company's yard. The method followed was to close one end of a piece of pipe, and then throw water into it by a forcing pump attached to the other end, the force or pressure being measured by a gauge belonging to the pump. When the water from the injecting pump first begins to press out the pipe, little or no alteration is observed on it for some time. As the operation proceeds, however, the pipe gradually swells throughout its whole length, until at last a small protuberance is observed rising in some weak part, which increases until the substance of the pipe becoming thinner and thinner, is at last rent asunder, when the pipe bursts with a crash, and the water issues with great violence.

In the first experiment, the pipe was of 1 inch bore, and the metal, which was remarkably soft and ductile, one-fifth of an inch in thickness. This sustained a power equivalent to that of a column of water 1000 feet high, equal to 30 atmospheres, or 420lbs. per square inch of internal surface, without alteration; but with

a pressure equal to 1200 feet of water it began to swell, and with 1400 feet, or 600 lbs., on the square inch, it burst. When measured after the experiment, it was found to have swelled until of a diameter of 1 of an inch. The edges of the fracture were not ragged, but smooth and sharp like a knife.

In a second experiment the pipe was two inches in diameter, and one-fifth of an inch in thickness. It sustained a pressure equal to that of a column of water 800 feet in height with hardly any swelling, but with 1000 feet it burst. The fracture here was not so fine as in the former pipe, the metal being much less ductile. Caledonian Mercury.

3. Method of curing Smoky Chimneys.-There is a way of building a vent, which was found to succeed in the huts which were erected by the British army in America during the war of the revolution; and even in the underground vents which were built to their tents when out at a late period of autumn, or rather the beginning of winter. In the writer's own house, where the principal vents were altered upon this plan after the house was finished, and in which there have been fires for nine months, the purity and cleanliness of the rooms sufficiently testify its efficacy; but he has a still farther proof in the testimony borne to it by Mr. Elliot, who built the house and made the alterations, and who was so convinced of the improvement effected from what he saw, while the vents were damp, that in the two houses which he has since built in Melville-street, Edinburgh, he has constructed all the vents on the same principle. The method is simply to contract the vent as soon as possible, then gradually to widen it for 4 or 5 feet, and then again contract it to the usual dimensions, and carry it up in any direction. No register grates are necessary.-New Monthly Mag. xv. 456.

4. Suggested Improvements in Light-houses.-Although great improvements have of late years been made through the British dominions upon light-houses, yet it is possible to make further progress in so useful and necessary a building. They may be so constructed as not only to ascertain the situation of head-land, harbours, &c.; but also to determine the distance the observer may be from them in the following manner, viz.-Suppose the lighthouse to be erected of a conical form, the great light at the top may have what tinge it shall be thought proper to give it ; underneath, at a distance of from 100 to 150 or 200 feet, three more smaller lights to be seen a few leagues at sea. So long as these last-mentioned are not seen, the observer may conclude he is a considerable distance from the light-house; but as soon as any one of them is perceivable, he need only take the angle of altitude between it and the great one, and in a table calculated on purpose