Page images

of these tertiaries in the so-called London and Hamsphire basins as areas of deposit*. It is not necessary to go over the grounds for the proof of that which has long been admitted. It is well known that Sir Charles Lyell long maintained a theory of the rise and denudation of the Weald, on the like notion of the gradual removal of the materials into the basins or synclinals on either side. This is now withdrawn and another substitutedt, which the author allows to be provisional and tentative, in part at least.

In the early essay to which I refer, I showed that the Weald Valley had no existence during the deposit of the tertiaries, and that consequently the area of these deposits was much greater than the synclinals in which they are now found. What was the full extent of that area it is not now necessary to inquire.

There are good grounds for believing that it extended over all that is now the south-east part of England, and also over a large part of the adjoining continent. We know, too, that it must have been diversified with sea and dry land. Dry land could not have been far distant when the flora of Sheppey was produced. And the same may be predicated of the copious supply of fossil wood, the ophidians, and the numerous mollusca of Bracklesham of a later date. Be this as it may, a change comes over the scene ;-we part with the pleasant climate of one, and the happy fauna of the other; the mountainous parts of Britain are covered with glaciers; the south-eastern part of England and great part of the north of Europe are occupied by an arctic ocean, and the glacial period is established f.

The arguments used to prove that the Weald excavation could not have been in existence when the tertiaries on each side of it were deposited, are equally potent in proof of the non-existence of the same excavation anterior to the glacial period. A slight examination of the phænomena of surface arrangement and of levels will determine these points, and show that the deposit of the boulder drift was anterior to the date of the Weald Valley.

The Arun, the river nearest Selsey on the Sussex coast, is a tidal river up to Pulborough, fifteen miles inland. By the profile of the country here given, we see that the boulder drift lies at Selsey high above the sea-levelş. Without being over nice in detail, we are pretty well assured that if the water on the coast always stood at high tide, the levels at Pulborough, and hundreds of square miles beside, would be constantly flooded.

It is obvious, therefore, that the glacial sea which deposited


* A Geological Memoir on Western Sussex, &c., 1828. + Manual, p. 272 et seq. | Manuals and Systems of Geology and Geological Journals, passim. Ś Selsey is 26 feet above the sea.

the boulders at Selsey must have occupied the Weald, and left

[blocks in formation]

traces of its presence, as it has done in the valley of the Thames and on the coast of Sussex, if the Weald had been in existence. The case is still stronger taking the levels of the Highgate Hills, or the site of Stonehenge and Salisbury Plain : unless, indeed, it be insisted on, that the coast-line has sunk whilst the inner country has risen, or vice versa ; or that the boulders which once covered the Weald have melted away by atmospheric erosion,both propositions too bold even for the most plastic schemes of modern geology. With the help, then, of the boulder drift we are brought to the conclusion that the upburst of the Wealden and the rise of the whole anticlinal were posterior to the æra of the northern drift, and the transport by icebergs in this part of the world.

Under what circumstances we parted with the climate of the glacial period we need not now inquire. The tertiary deposits were still persistent on the chalk, and the boulder drift over all. Whether we had here an archipelago or an open ocean, a dislocation takes place, whether subaërial or subaqueous, or partly both, is immaterial; the anticlinal line about which so much has been said suddenly rises, the two great synclinals on either side are brought into existence, and we have the commencement of the

Diluvial Epoch. My exposition of the evidence in favour of the violent excavation of the Weald by the joint operation of earthquake and diluvial currents is already in print, and it is unnecessary to reproduce the proofs in this place: I shall briefly make allusion to some of the points.

Mr. Hopkins has given us to understand, that the first upburst of the Wealden strata at least had a character of totality. And he adduces proofs from mathematical and mechanical prin. ciples, of a unity and synchronism in the fissures, both longitudinal and transverse, which he has traced out there. In the map which accompanies Mr. Hopkins's memoir on this subject (Trans. of Geol. Soc. vol. vii.), he has erroneously drawn an imaginary line of demarcation round what he calls the “disturbed district," although I had already shown that the same phænomena of dislocation and disturbance had been continued on westward of that line, or in other words, west of the Alton Hills. Mr.

Hopkins has not himself drawn any erroneous conclusions from this mistake, but others have*.

The conclusions this gentleman drew from his mechanical theory of fissure I had already arrived at from surface phænomena,-the arrangements of longitudinal and transverse valleys, the watershed and drainage.

On both of his expositions of the theory of the Weald denudation, Sir C. Lyell has given me credit for pointing out the opposing river gorges in the chalk as indicative of the direct extension of the lines of fissure on which these gorges were formed directly from side to side. I never laid much stress on this point; but when I drew attention to it, I was not aware that an instance of this kind existed in its original integrity. It is the more valuable, because it occurs in the westernmost part of the anticlinal, and may be considered as the very experimentum crucis of this theory of transverse drainage.

The drainage of the Vale of Pewsey is brought to its lower end to form the Wiltshire Avon. The Avon here enters a chalk gorge, traverses the whole breadth of Salisbury Plains in a direct line, through a series of little valleys which could only have originated in a transverse fissure, passes by Salisbury, enters the tertiary country, and then runs direct to Christchurch. This line of drainage is beautifully laid down in Mr. Greenough's map.

Coming nearer home, the most perfect example of drainage by transverse fissure, in a direct line through all the tough and stony strata of the Weald, is afforded by the Arun. This river takes its rise by two sources, one on each side of Horsham Forest. These unite about a mile west of the town of Horsham, and the united stream takes its course westward along the very centre of the axis of the Weald till it reaches Rudgwick. It then turns suddenly southward and runs in a direct line to Arundel Haven, traversing transversely, as before said, all the courses of the Wealden, the greensand, and the chalk, in a course of twenty miles.

Removal of Materials. The Royal Society is said to be now engaged in an inquiry into the force and motive power of earthquake-waves. Till we derive more certain information from that source, we must be content with some proximate data of the power of aqueous currents over solid materials afforded by the information occasionally drifted in from various sources ;—such as the great débâcle of the Drance which occurred a few years ago, the Moray floods, the earthquake-waves of the coast of Chili, of Scilla in Calabria, and of what have lately occurred in Japan. To those who may doubt of the power of aqueous currents forcibly and suddenly to remove the solid materials we know to have been lost from the Weald, I submit these considerations. It may be difficult to conceive a motive power in running water equal to the removal of great rock-masses without the help of ice, like the boulder, for instance, mentioned by Mr. Godwin Austen, lying on the coast at Pagham near Selsey, computed to weigh thirty tons. No earthquakewave would float, and none perhaps propel such a mass. But if the bed on which the boulder lay was moved, that would move also. Smeaton the engineer, in his autobiography, tells us that he was employed to build a bridge on one of our northern rivers (I quote from memory), -I think it was either the Wear or the Tyne,-where no bridge had hitherto been able to withstand the floods. Smeaton built his bridge, as he supposed, of sufficient strength to withstand any flood to which it could be subjected. It happened soon after that a contingency of rapid thaw and rain produced a flood equal, if not superior, to all former precedent. The engineer was on the spot to watch its effect, and had the mortification to see his bridge swept away before his face. But this eminent man found consolation in the assurance by proof, after the water had subsided, that his bridge was not broken down, but that the bed of the river was actually scooped out and the whole carried away together.

* We may suppose that Mr. Hopkins meant the line of demarcation only as the boundary of the country he had himself explored.

It is with these considerations in his mind I recommend the geologist to examine the lacerated escarpments of the Weald, to study the entrances to the stone-quarries of Boughton or Maidstone, to examine the combs of Hascomb, of Henly Hill, or the transverse gorges of the rivulets which traverse the greensand escarpments, and he will see how such masses have been torn away, or are now lying as if torn away and prepared for removal. The question here is not,-Were not these materials capable of removal by gradual sea-board erosion? The question is,—Were they so removed? With such signs of violent disruption around us, a reply in the affirmative is impossible.

[To be continued.)

[ocr errors]

VI. On the Action of Nitric Acid on Alcohol at common Tempe

ratures.-Second Memoir. By Dr. H. DEBUS*. IN N the November Number of the Philosophical Magazine I

described the preparation of a peculiar aldehyde produced along with glyoxylic acid by the action of nitric acid on alcohol. After the action had ceased, the still acid liquid was evaporated on the water-bath to the consistency of a thick syrup. This residue consisted of glycolic, glyoxylic, and oxalic acids, and of a member of the same class of compounds to which the aldehyde of acetic acid belongs. It was dissolved in water and neutralized with carbonate of lime. On addition of alcohol, the glycolate and glyoxylate of lime precipitated almost entirely, whilst the aldehyde remained in solution. The filtrate from this precipitate was evaported on the water-bath; the aldehyde remained as a thick syrup of a slight brown colour. It was soluble in æther,

* Communicated by the Author.

. except a small quantity of brown resinous matter. The ætherial solution left, after filtration and distillation at 100° C., a solid, transparent, and amorphous substance of a slight yellow colour. This residue consisted almost entirely of the aldehyde of glyoxylic acid; I propose to call it Glyoxal, Co H*03*.' It is isomeric with glycolic acid, and bears the same relation to glyoxylic acid as the aldehyde C? H40 to acetic acid.

The strong aqueous solution of this substance was mixed with five or six times its bulk of a concentrated solution of bisulphite of soda. After about three hours' standing, a large quantity of crystals formed around the sides of the bottle in which the mixture was kept.

These crystals were dissolved in as little boiling water as possible, and the clear liquid allowed to cool gradually. Prismatic crystals of a compound of

Glyoxal with bisulphite of soda, 2(Na HO.S02), C? Ho OS, were obtained. From the mother-liquor, on addition of alcohol, another quantity of the same substance precipitated, which, if not quite pure, was recrystallized in the same manner. This compound forms white and hard crystals, easily soluble in water, but almost insoluble in alcohol. The aqueous solution turns slightly yellow on continued boiling; it precipitates acetate of lead and chloride of barium. Hydrochloric and diluted sulphuric acids decompose it very slowly, generating sulphurous

cid. Nitric acid oxidizes very rapidly the bisulphite of soda into bisulphate, and the glyoxal into oxalic acid.

Analysis gave the following results :

I. 0.625 grm., burnt with chromate of lead, gave 0:1935 grm. carbonic acid and 0:122 grm. water.

[ocr errors]

0:622 grm. gave 0.311 grm. sulphate of soda. II. 0.8825 grm. gave 0:2735 grm. carbonic acid and 0.1730

grm. water.

0:478 grm. gave 0.237 grm. sulphate of soda. 0.729 grm., oxidized with a mixture of chlorate of potash and

* C=12, H=1, 0=16.

« PreviousContinue »