Page images

Electric Deflagrations.

Mr. Mason, of High Holborn, who is an exceedingly dexterous experimenter, has lately discovered a method of enhancing the beauty and splendour of charcoal deflagrations by voltaic electricity. He powders bichromate of potash and places the powder on the points of the charcoal, and when the latter has become red hot, the bichromate also enters into deflagration. The light produced is two-fold that given by the charcoal alone. The potash becomes decomposed and the liberated potassium scintilates in a very beautiful manner. We have seen Mr. Mason produce a beautiful effect with a battery of only thirty small jars.

Speaking of deflagrations, perhaps it may be interesting to some of our readers to know that the laminated inetals, such as gold, silver, or copper leaf, &c., give a good effect when deflagrated on a strip of bright tin plate, which may be connected with one pole of the battery, whilst the metallic leaf, placed on a long copper wire in connexion with the other pole, is passed gently over its surface. Gold gives the feeblest light, copper next. The light from white Dutch metal is much more brilliant, and of a pale purple tinge. That from silver is exceedingly handsome, being a pale greenish yellow. We have, for many years, used zinc turnings for deflagrating at the lecture table. They burst into a complete blaze, and become converted into philosophical wool, which floats in the air for a long time afterwards.

Case Hardening.


At the British Institution of Civil Engineers the conversion of iron into steel was discussed, and it was stated that iron could be converted into steel by immersion in pure carbon, as in the Macintosh process, at the rate of th of an inch per hour. Mr. Roberts stated that the success of case hardening depended on the gentleness of the heat. Great care must be taken not to overheat, and case hardening might take place to the depth of ths of an inch in four or five hours. It was stated to be cyanogen united with iron which produces case hardening, but carbon which produces steel. An instance was mentioned by Mr. Carpmael in which animal charcoal was used for case hardening the interior, and vegetable charcoal for softening the exterior. Allusion was made to the fact, that the most perfect chill is obtained by the employment of moulds red hot.

Progress of Physical Science.

Inst. Civ. Eng.

On the Origin of the Vegetation of our Coal Fields and Wealdens.* By J. T. BARBER BEAUMONT, ESQ., F. G. S.

A visit which I made during the last summer to the fossil trees recently discovered, apparently standing, as they grew, and rooted in an upper seam of coal in the line of the Bolton and Manchester Railway, has confirmed me in an opinion which I have always entertained, that the adopted theory of our coal-fields and wealdens being ancient deposits of trees in rivers and estuaries, is erroneous. The visible appearances to the contrary are now so many, and the anomalies they form to the doctrine taught are so puzzling *This paper was read at the meeting of the Geological Society, on the 20th day of November.

VOL. XXV.-No. 3-MARCH, 1840.


to young geologists, that I think it high time that this theory should be reconsidered. I think the facts prove, that in no instance is it likely that these formations arise from drifted trees sunk to the bottoms of mighty rivers and estuaries, but, on the contrary, that the coal vegetations grow where they are found, and that these places were the surfaces of small islands.

The adopted theory supposes that the coal-fields occupy the bed of "a mighty river or estuary," into which trees have been drifted and deposited; and that the alternating strata of coals and shale have resulted from successive deposits of plants, and of clay, sand, &c. Drifted trees in the deltas of some of the largest rivers are referred to as typical of these ancient masses of vegetation; and it is observed, that the coal formations and wealdens extending over Great Britain and the north of France do not much exceed the extent of the delta of the Mississippi or the Niger.

The first observation that strikes me on this theory seems fatal to its existence in toto. A mighty river or delta could only have existed in a mighty continent a small continent would not do; there is no very mighty river or delta in Europe. Then the coal strata (near Newcastle) with the intermediate shale, are collectively 580 yards in thickness; the first deposit, therefore, must have been in a river or delta of that depth, which is about six times the mean depth of the German Ocean! What a continent there must have been to have produced a river or delta so wide and so deep! Such a continent we might reasonably expect would leave an abundance of fossils on its surface, as well as at the bottom of its great river; we ought to see fossilified timber trees, and bones of continental quadrupeds, for hundreds of leagues around; but, with a few exceptions of small extent, not a single timber tree, not a trace of a land animal is any where discovered. This absence of land fossils, I submit, is proof positive, geologically speaking, that there could have been no extensive continent within which the supposed river or delta was formed; but the proof goes further-all this land, for hundreds of leagues around the coal and the wealden vegetations, swarms with the remains of marine animals, in addition to marine plants, and nothing else it is visibly ancient sea-bed.

But let us look at the composition of the actual coal-fields; not a large timber tree, or bone of a land quadruped is to be found in them; all that we see are masses of fern, rushes, canes, and the like, except in the upper strata, on which coniform trees are found, some of them in their growing position; but the principal beds extend for many miles, nearly of an uniform thickness, generally of only a few feet, and sometimes of only a few inches. It is truly stated, "The surface of these strata shows the bending branches, with their delicate apparatus of foliage, almost in the beauty and vigour of their primeval life." But if the strata were formed from drifted and sunken timber trees-and such, I submit, would not have failed to be supplied by an extensive continent-some massive trunks of trees would have occurred to disturb the uniformity of the thin coal seams. The superincumbent pressure did not flatten "the festoons of graceful foliage," or "bending branches," for they arise above the coal strata, and mingle with the shale over them. That pressure, therefore, could not have crushed the trunks and roots of timber trees to obliteration, had any existed, within the thickness of the coal seams; but the evenness of the coal strata is unbroken by any trunks and roots of timber trees. This, I think, completes the proofs that the coal seams could not have been composed of drifted trees, sunk in the depths of a mighty river. There is also natural evidence against the

vegetations being formed from sunken trees of any kind, in the vigour and freshness of their appearance; while in that state they would not have sunk at all, but have floated out to sea, as at the present day timber trees from America drift on our own coasts. To have sunk in the deep river they must have first rotted! But this could not have been, for the foliage is found with the "freshness and vigour of primeval life." Moreover, drifted trees are stopped in deltas from the shallowness of the water being insufficient to float them on; we know of no deposits of trees in deep water.

An eminent geologist, seemingly aware of the necessity of providing a continent for this great river or estuary, supposed that it might have been in the German Ocean; while another eminent professor, to whose labours the public are greatly indebted, finding that area too small, crosses to the other side, and speculates on the possibility of its having been in the Atlantic Ocean. But the speculations of there having been a mighty continent in an ocean far off to the east or to the west of our great river or estuary, is of no use whatever; to help the case, the continent must have actually encompassed the river or estuary; but all around the supposed river deposits, for hundreds of leagues, has been visibly sea-bed! There can be no river, mighty or minute, in a sea-bed. Further evidence and argument, in disproof of this theory, therefore, seems unnecessary.

In offering an opinion upon what really has been the origin of the coalfields and wealdens, I shall be more diffident, and very brief. To my understanding, they appear to have been swampy islands. It is reasonable to believe, that on the first elevation of the rocks, while some stood high above the ocean, others would be nearly level with its surface, and that disjoined fragments and drifted clay, sand, and shells, would accumulate into islands; these would give rise to a profuse growth of marsh plants, which decaying and regenerating, others would accumulate, in the manner of peat bogs, to various heights; and ferns, palms, calamites, and coniferous trees, in some positions, would acquire a gigantic growth. It seems not unreasonable also to conceive, that after the great bursting up of the crust of the earth, large cavernous hollows would be left, and that there would be many settlements in the broken crust before it finally subsided. An island, sunk beneath the ocean's surface by one of these settlements, would be covered with drifted clay, sand, and shells, and the tall cany trees upon it, if any, be broken down by the waves and detritus; new accumulations would again raise its surface above the ocean, somewhat like our coral islands; a fresh growth of plants would then take place, and then another settlement, and so on to the number of coal seams and shale that compose a formation. The coal seams and shale in some places, as near Newcastle, are unusually repeated, but repeated settlements of the surface would be no more than consistent with the extraordinary uplift they succeeded-in some cases also, depressions of the surface may have been followed by partial uplifts. Of such sighings of the earth we have examples even in our own time: the temple of Serapis is not one of the most modern.

The wealdens are still more easily recognised as ancient islands, raised after the coal-making heat and influence had gone by; we have only to suppose the coal and wealden herbaria to be as they most frequently present themselves to our eyes, the growth of the lands where we find them, instead of imagining them to be drifted deposits from an inconceivable continent to the bottom of a mighty but impossible river, and all the appearances about them will cease to perplex.

Mining Jour.

On an anomalous Electric Condition of Iron. By MARTYN I. ROBERTS, Esq.

It is now some months since, that while prosecuting a series of novel galvanic experiments, I discovered a singular anomaly in the electric condition of iron, which is, that although iron if associated with copper as a galvanic pair is highly positive to the copper, yet when associated with zinc, it is more highly negative to the zinc than copper would be under similar circumstances; or in other words, that although copper and iron form a galvanic combination, in which the iron is in the same relation to the copper that a zinc plate would be, yet that iron and zinc form a galvanic pair that has a greater power of generating electric action than a similar sized pair of copper and zinc. This singular phænomenon will, I believe, lead the way to some important discoveries; but not to occupy too much space in your valuable Journal, I will without further comment give extracts from my note-book of some experiments made by me on this subject.

Jan. 1st, 1839. A galvanic combination of iron and zinc was put in communication with two poles of a differential galvanometer; a like-sized combination (or gal. pair) of copper and zinc was connected with the other two poles of the diff. galvanometer: Deviation of needle in favour of the iron and zinc pair 25 degrees.


Feb. 27, 1839. Experiments made on the comparative power of two galvanic batteries fitted up on Wollaston's plan (that is with the negative plate opposed to both surfaces of the zinc or positive plate.) The size of the plates was the same in both batteries, viz. zinc plate 2 inch. by 2 inch. The number of pairs in each battery was ten. The only difference between the two batteries was, that the negative plates in one were of copper and in the other of iron.

The exciting solution was dilute sulphuric acid, which was not renewed during the experiment, but the experiment was continued until the acid was exhausted. The power of each battery was applied to the decomposition of water, and the gas collected was the measure of the power.


Battery of Copper and Zinc.

The first cubic inch of gas obtained
Then one half cubic inch


in 33 minutes.
in 92 minutes.

Acid was now exhausted. 1 cubic inch in 125 minutes.

[merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]

Iron battery with a measured quantity of acid gave 4 cubic inches in 104 minutes.

Copper battery with a like quantity of acid gave only 1

125 minutes.

cubic inch in

L. & E. Philos. Mag.

Microscopic Geology.

Professor Ehrenberg, already so justly famed for his microscopic discoveries in the animal and vegetable kingdoms, has recently added fresh lustre to his name by the pursuit of geological science. He has discovered that large masses of rock, and even whole strata of the earth are entirely composed of the remains of microscopic animals. The soft internal parts of these animalcules were, during life, covered with a tegument or case, composed of silica or flint; these earthly integuments have hitherto resisted decomposition, and now, in countless myriads, compose large portions of the globe. The cases are for the most part cylindrical, with transverse markings, and so hard, that the rocks composed of them are used as polishing stone. Of about eighty species of fossil infusoria which have been discovered in various strata, about one-half are identical with those which still exist in the waters; so that these classes of invisible creatures have a durability which has been denied to larger forms of life. Professor Ehrenberg has discovered that these microscopic animals exists at present in such abundance, under favourable circumstances, that there is no difficulty in accounting for the presence of the immense masses of their fossil remains. In the public garden at Berlin, workmen were employed for several days in removing wheelbarrows full of materials which consisted entirely of them. Ehrenberg has also succeeded in producing from masses of the living animals, tripoli and polishing slate, similar to the rocks from which he had originally obtained the remains; and he has added another to the numerous proofs of the correctness of the modern theories of geology, by showing that, while the microscopic contents of the more recent strata are all fresh-water infusoria, those of the chalk are animals which must, or at least could, have lived in the ocean. These discoveries were the result of great labour. Professor Ehrenberg had made a study of recent infusorial animalcules, during many years; and when his attention was drawn to the subject of fossil infusoria by M. Fisher, in 1836, he was able to recognise at once many species, which, in a living state, had been long familiar to him. Specimens of the rocks to which we have above alluded, and of the infusoria which compose them, are at present to be found in most of the mineralogical collections of Great Britain.-The European.

Mining Jour.

New Theory of the Tides. By PROF. WHEWELL. Cambridge Philosophical


At a meeting of this Society on the evening of Monday the 11th of November (Dr. Hodgson, the President, being in the chair), Mr. Whewell explained a new theory of the tides. The phænomena of the tides have hither. to been referred to the equilibrium theory, the elevation of the waters which occasions the tide being compared with the elevation which the moon would produce in the ocean if the earth and moon were both at rest. But the general motion of the waters of the ocean does not countenance this theory, or allow us to suppose that a fluid elevation resembling that of the equilibrium spheroid follows the moon from east to west; for the Pacific, the largest ocean, has no tide in its central parts; and at its eastern shore, near Cape Horn, the tide wave runs from west to east, although there is nothing to prevent its following its natural course.

The new theory which was offered was this:-The tide of each large

« PreviousContinue »