Essay on the Theory of the Earth

by baron Georges Cuvier

ON THE ALLUVIAL LAND OF THE DANISH ISLANDS IN THE BALTIC, AND ON THE COAST OF SLESWIGH.

In this section, Cuvier gives a clear and distinct account of several kinds of alluvial formations. M. De Luc, in the first volume of his Geological Travels, describes the alluvial formations that cover and bound many of the islands in the Baltic, and upon the coast of Denmark, and gives so interesting an account of the modes followed by the inhabitants, in preserving these alluvial deposites, that we feel pleasure in communicating it to our readers.

“During my stay at Husum, I had the advantage of passing my evenings very agreeably and profitably at the house of M. Hartz, with his own family, and two Danish officers, Major Behmann, commandant at Husum, and Captain Baron de Barackow. The conversation often turned on the objects of my excursions, and particularly on the natural history of the coasts and of the islands; respecting which, M. Hartz obligingly undertook to give me extracts from the chronicles of the country. This led us to speak of the Danish islands; and those officers giving me such descriptions of them, as were very interesting to my object, I begged their permission to write down, in their presence, the principal circumstances which they communicated to me. These will form the first addition to my own observations; I shall afterwards proceed to the information which I obtained from M. Hartz.

The two principal islands of the Danish Archipelago, those of Funen and Seeland (or Zeeland), as well as some small islands in the Kattegate, namely, Lenoe, Anholt, and Samsoe, are hilly, and principally composed of geest[379]; and in these are found gravel and blocks of granite, and of other stones of that class, exactly in the same manner as in the country which I have lately described, and its islands in the North Sea. On the borders of the two first of these Danish islands, there are also blocks in the sea; but only in front of abrupt coasts, as is the case with the islands of Poel and Rugen, and along the coasts of the Baltic. The lands added to these islands of geest are in most part composed of the sand of the sea, the land-waters there being very inconsiderable; and to the south of them have been formed several islands of the same nature, the chief of which are Laland and Falster, near Seeland. These, like the marsh islands in the North Sea, are sand-banks accumulated by the waves, and, when covered with grass, continuing to be farther raised by the sediments deposited between its blades. In the Baltic, where there are no sensible tides, such islands may be inhabited without dikes, as well as the extensions of the coasts; because, being raised to the highest level of that sea, while their declivity under water is very small, and being also more firm in their composition, the waves die away on their shores; and if, in any extraordinary case, the sea rises over them, it leaves on them fresh deposits, which increase their heights. These soils are all perfectly horizontal, like those added to the coasts of the Continent.

Some of these islands approach entirely, or in part, to the nature of that of Rugen. This island of Seeland, on that side which is called Hedding, has a promontory composed of strata of chalk with its flints. The island of Moen (or Mona), on the south of the latter, has a similar promontory near Maglebye and Mandemark; and the island of Bornholm, the easternmost of those belonging to Denmark, contains strata of coal, covered by others of sandstone. Phenomena like these, evident symptoms of the most violent catastrophes at the bottom of the ancient sea, proceeding, as I think I have clearly shewn, from the subsidence and angular motions of large masses of strata, which must have forced out the interior fluids with the utmost impetuosity, it is not surprising that so many fragments of the lowermost strata are found dispersed over this great theatre of ruins.

I now proceed to the details which I received from M. Hartz; beginning by a specific designation of the islands dependent on the province of Sleswigh, such as they are at present, belonging to the three classes already defined. To commence from the north; Fanoe, Rom, Sylt, and Amrom, were originally islands of the same nature as the neighbouring continent, but have been since extended by marsches[380]. The soil of these islands, with its gravel and blocks of primordial stones, was at first barren, as the geest is naturally every where; but is become fertile by manure, of which there has been no deficiency, since those grounds have been surrounded with marsch, where the cattle are kept in stables during the winter. In the island of Sylt, there are spaces consisting of moor, but its head of land, which extends on the south as far as Mornum, is composed entirely of marsch, and is bordered with dunes towards the open sea, because, the sediments of the rivers not reaching any farther, the sea-sand impelled against it by the waves remains pure, and is thus raised by the winds in hillocks on the shore. The shallow bottom of the sea, between this island and that of Fora, is of geest: at low water, it may be passed over on foot; and there are found on it gravel and blocks of granite. But on the same side of Fora there is a great extent of marsch, beginning from St Laurencius. Among the islands consisting entirely of marsch and surrounded with dikes, the most considerable are Pellworm and Nord Strand; and among the Halligs, or those inhabited without dikes, the chief are Olant, Nord-marsh, Langne, Groode, and Hooge.

Such are the islands on this coast, in their present state, now rendered permanent by the degree of perfection at which the art of dike-making is arrived. But, in former times, though the original land was never attacked by the sea, which, by adding to it new lands, soon formed a barrier against its own encroachments, the latter, and the islands composed of the same materials, were subject to great and sudden changes, very fatal to those who were engaged to settle on them by the richness of their soil, comparatively with the continental. The inhabitants, who continued to multiply on them during several generations, were taught, indeed, by experience, that they might at last be invaded by the element which was incessantly threatening them; but having as yet no knowledge of natural causes, they blindly considered those that endangered them as supernatural, and for a long time used no precautions for their own security. They were ignorant of the dreadful effects of a certain association of circumstances, rare indeed, but, when occurring, absolutely destructive of these marsches. This association consists of an extraordinary elevation of the level of the North Sea, from the long continuance of certain winds in the Atlantic, with a violent storm occurring during the tides of the new or full moon; for then the sea rises above the level of all the marsches; and before they were secured against such attacks, the waves rolling over them, and tearing away the grass which had bound their surface, they were reduced to the state of mere banks of sand and mud, whence they had been drawn, by the long course of ordinary causes. Such were the dreadful accidents to which the first settlers on these lands were exposed; but no sooner were they over, than ordinary causes began again to act; the sand-banks rose; their surface was covered with grass; the coast was thus extended, and new islands were formed; time effaced the impression of past misfortunes; and those among the inhabitants of these dangerous soils, who had been able to save themselves on the coast, ventured to return to settle on them again, and had time to multiply, before the recurrence of the same catastrophes.

This has been the general course of events on all the coasts of the North Sea, and particularly on those of the countries of Sleswigh and Holstein. It is thus that the origin and progress of the art of dikes will supply us with a very interesting chronometer in the history of the continent and of man, particularly exemplified in this part of the globe. A Lutheran clergyman, settled in the island of Nord Strand, having collected all the particulars of this history which the documents of the country could afford, published it in 1668, in a German work, entitled The North Frisian Chronicle. It was chiefly from this work, and from the Chronicle of Dankwerth, that M. Hartz extracted the information which he gave to me, accompanied by two maps, copied for me, by one of his sons, from those of Johannes Mayerus, a mathematician; they bear the title of Frisia Cimbrica; one of them respecting the state of the islands and of the coast, in 1240, as it may be traced in the chronicles, and the other, as it was in 1651.

According to these documents, the first inhabitants of the marsches were Frisii or Frisians, designated also under the names of Cimbri and Sicambri: the latter name, M. Hartz conjectures, might come from the ancient German words Seekampfers, i. e. Sea-warriors; the Frisians being very warlike. These people appear to have had the same origin with those, who, at a rather earlier period, took possession of the marsches of Ost-Frise (East-Friesland), and of that Friesland which forms one of the United Provinces; but this common origin is very obscure. Even at the present day, the inhabitants of the marsches, from near Husum to Tondern, or Tunder to the North, though themselves unacquainted with it, speak a language which the other inhabitants of the country do not understand, and which is supposed to be Frisian. It is the same at a village in the peninsula of Bremen, by which I have had occasion to pass.

The Sicambri or North Frisians, are traced back to some centuries before the Christian era. At the commencement of that era, they were attacked by Frotho, King of Denmark, and lost a battle, under their king Vicho, near the river Hever. Four centuries afterwards they joined the troops of Hengist and Horsa. In the year 692, their king Radebot resided in the island of Heiligeland. Charles Martel subdued them in 732; and some time afterwards they joined Charlemagne against Gottric, King of Denmark. These are some of the circumstances of the history of this Frisian colony, recorded in the chronicles of which I have spoken; but the history here interesting to us is that of the lands whereon they settled.

It appears that these people did not arrive here in one body, but successively, in the course of many years: they spread themselves over various parts of the coasts of the North Sea, and even a considerable way up the borders of the Weser and the Elbe; according to documents which I have mentioned in my Lettres sur l’Histoire de la Terre et de l’Homme. These new settlers found large marsches, formed, as well in the wide mouths of those rivers as along the coasts, and around the original islands of geest; especially that of Heiligeland, the most distant from the coast, and opposite the mouth of the Eyder. Of this island, which is steep towards the south, the original mass consists of strata of sandstone; and at that time its marsch extended almost to Eyderstede: there were marsches likewise around all the other original islands; besides very large islands of pure marsch in the intervals of the former.

All these lands were desert at the arrival of the Frisians; and the parts on which they established their first habitations, to take care of their breeds of horses and cattle feeding on the marsches, were the original eminences of the islands; on that of Heiligeland they built a temple to their great goddess Phoseta, or Fosta. When they became too numerous to confine themselves to the heights, their herds being also greatly multiplied, they ventured to begin inhabiting the marsches; but afterwards, some great inundations having shewn them the dangers of that situation, they adopted the practice followed by those who had settled on the marsches of the province of Groningen, and still continued on the Halligs; that of raising artificial mounts called werfs, on which they built their houses, and whither they could, upon occasion, withdraw their herds; and it likewise appears, that, in the winter, they assembled in greater numbers on the spots originally the highest, in the islands, as well as on some parts of the coasts.

Things continued in this state for several centuries; during which period, it is probable that the inhabitants of these lands were often, by various catastrophes, disturbed in the enjoyment of them, though not discouraged. But in 516, by which time these people were become very numerous, more than 600 of them perished by one of the concurrences of fatal circumstances already defined. It was then that they undertook the astonishing enterprise of enclosing these lands. They dug ditches around all the marsches, heaping up on their exterior edge the earth which was taken out; and thus they opposed to the sea, dikes of eight feet in height. After this, comprehending that nothing could contribute more to the safety of their dwellings, than to remove the sea to a greater distance, they undertook, with that view, to exclude it from the intervals between the islands, by uniting, as far as should be possible, those islands with each other. I will describe the process by which they effected this, after I shall have recalled to attention some circumstances leading to it.

From all that I have already said of the fore-lands, and of the manner in which they are increased, it may be understood, that the common effects of the waves and of the tides is to bring materials from the bottom of the sea towards the coasts; and that the process continues in every state of the sea. The land winds produce no waves on the coasts, which can carry back to the bottom of the sea what has been brought thence by the winds blowing against the shore; and as for the tides, it may have been already comprehended (and shall soon be proved), that the ebb carries back but very little of what has been brought by the flood. So that, but for some extraordinary circumstances, the materials continually impelled towards the shore, which first form islands, would at last unite against the coast in a continuous soil. The rare events, productive of great catastrophes, do not carry back these materials towards the bottom of the sea; they only, as it has been said before, ravage the surface, diminishing the heights, and destroying the effect of vegetation. These, then, were the effects against which it was necessary to guard.

I now come to the plan of uniting the islands, formed by these early inhabitants. They availed themselves for that purpose of all such parts of the sand-banks as lay in the intervals between the large islands, and were beginning to produce grass. These, when surrounded with dikes, are what are called Hoogs; and their effects are to break the waves, thus diminishing their action against the dikes of the large islands, and, at the same time, to determine the accumulation of the mud in the intervals between those islands. In this manner a large marsch island, named Everschop, was already, in 987, united to Eyderstede by the point on which Poppenbull is situated; and in 995, the union of the same marsches was effected by another point, namely, that of Tetenbull. Lastly, in the year 1000, Eyderstede received a new increase by the course of the Hever, prolonged between the sand banks, being fixed by a dike; but the whole still remained an island. This is an example of the manner in which the marsch islands were united by the hoogs; and the chronicle of the country says, that, by these labours, the islands were so considerably enlarged in size, and the intervals between them so much raised, that, at low water, it was possible to pass on foot from one to the other. The extent of these marsches was so great on the coast of Sleswigh alone, that they were divided into three provinces, two of which comprehended the islands, and the third comprised the marsches contiguous to the coast; and the same works were carried on upon the marsches of the coast of Holstein.

But the grounds thus gained from the sand-banks were very insecure; these people, though they had inhabited them more than ten centuries, had not yet understood the possibility of that combination of fatal circumstances above described, against which their dikes formed but a very feeble rampart; the North Sea, by the extraordinary elevations of its level, being much more formidable in this respect than the ocean, where the changes of absolute level are much less considerable. I shall give an abridged account of the particulars extracted by M. Hartz from the chronicle of Dankwerth, relative to the great catastrophes which these marsches successively underwent, previously to the time when experience led to the means necessary for their security.

In 1075, the island of Nord Strand, then contiguous to the coast, particularly experienced the effect of that unusual combination of destructive causes; the sea passing over its dike, and forming within it large excavations like lakes. In 1114 and 1158, considerable parts of Eyderstede were carried away; and in 1204, the part called Sudhever in the marsch of Uthholm was destroyed. All these catastrophes were fatal to many of the marsch settlers; but in 1216, the sea having risen so high that its waves passed over Nord Strand, Eyderstede, and Ditmarsch, near 10,000 of their inhabitants perished. Again, in 1300, seven parishes in Nord Strand and Pellworm were destroyed; and in 1338, Ditmarsch experienced a new catastrophe, which swept away a great part of it on the side next Eyderstede: the dike of the course of the Eyder between the sand-banks was demolished, and the tides have ever since preserved their course throughout that wide space. Lastly, in the year 1362, the isles of Fora and Sylt, then forming but one, were divided, and Nord Strand, then a marsch united to the coast, was separated from it.

During a long time, the inhabitants who survived these catastrophes, and their successors, were so much discouraged, that they attempted nothing more than to surround with dikes like the former such spaces of their meadow-land as appeared the least exposed to these ravages, leaving the rest to its fate. But the common course of causes continually tending to extend and to raise the grassy parts of the sand-banks, and no extraordinary combination of circumstances having interrupted these natural operations, later generations, farther advanced in the arts, undertook to secure to themselves the possession of those new grounds. In 1525, they turned their attention to the indentations made, during the preceding catastrophes, in the borders of the marsches; the waves, confined in these narrow spaces, sometimes threatening to cut their way into the interior part. In the front of all the creeks of this kind they planted stakes, which they interlaced with osiers, leaving a certain space between the lines. The waves, thus broken, could no longer do injury to the marsch; and their sediments being deposited on both sides of this open fence, very solid fore-lands were there formed. In 1550, they raised the dikes considerably higher, employing wheelbarrows, the use of which was only then introduced. For this purpose, they much enlarged and deepened the interior canals, in order to obtain more earth, not merely to add to the height of the dikes, but to extend their base on the outer side. At last they began to cover these dikes with straw-ropes; but this great preservative of dikes was at first ill managed; and the use of it was so slowly spread, that it was not adopted in North Strand and in Eyderstede, till about the years 1610 and 1612.

Before that time, however, the safety of the extensive soil of the latter marsch had been provided for in a different manner. I have said above, that, when the isles of Everschop and Utholm had been united to it, the whole together still formed but one large island; now, in this state, it was in as great danger on the side towards the continent, as on that open to the sea; because two small rivers, the Trene and the Nord Eyder, discharging themselves into the interval between it and the land, and by preserving their course to the sea, this interval was thus kept open to tempest, sometimes from the side of the Hever, sometimes from that of the Eyder; and the waves, beating against the geest, were thence repelled upon the marsch. The inhabitants, seeing that the expence of remedying these evils would be greater than they could afford, while at the same time it was indispensable to their safety, addressed themselves to their bishop and to their prefect, of whom they requested pecuniary assistance; and having obtained it they first undertook the great enterprise of carrying the Trene and the Nord Eyder higher up into the Eyder; keeping their waters, however, still separate for a certain space, by a dam with a sluice, in order to form there a reservoir of fresh water; the tides ascending up the Eyder above Frederickstadt. They were thus enabled to carry on the extremities of the dike on both sides to join the geest; and the interval between the latter and the marsch was then soon filled up, there being only left at their junction the canal above described which receives the water of the geest, and, at low water, discharges them from both its extremities by sluices. At the same time, the islands of Pellworm and Nord Strand were united with each other by means of eight hoogs; and the sandy marsches of which I have spoken, contiguous to the geest, on the north of that of Husum, were inclosed with dikes.

After the dikes had been thus elevated, and their surface rendered firm by the straw ropes, though the latter were not yet properly fixed, the inhabitants of the marsches for some time enjoyed repose; but on the 11th October 1634, the sea, rising to an excessive height, carried away, during a great tempest, the hoogs which had produced the junction between Pellworm and Nord Strand, these having ever since continued distinct islands; it also violently attacked Ditmarsch; and its ravages extended over the whole coast, as far as the very extensive new lands of Jutland. Princes then came forward zealously to the relief of their subjects. In particular, Frederick III., Duke of Sleswigh, seeing that the inhabitants of Nord Strand were deficient both in the talents and in the means necessary for the reparation and future security of that large island, and knowing that the art of dikes had made greater progress in Holland, because of the opulence of the country, addressed himself to the States-General, requesting them to send him an engineer of dikes, with workmen accustomed to repair them; and this was granted. The dikes of Nord Strand were then repaired in the most solid manner; and the Dutch engineer, seeing the fertility of its soil, advised his sons upon his death-bed, to purchase lands and settle there, if the Duke would grant them the free exercise of their religion; they being Jansenist catholics, and the inhabitants of the island Lutherans. The Duke agreed to this, on condition that they and their posterity should continue to superintend the works carried on upon the dikes; to which they engaged themselves. From that time the art of dikes, and particularly that part of it which consists in covering them solidly with straw, has become common to all the marsches; and the Dutch families, which have contributed to this fortunate change, continue to inhabit the same island, and to enjoy the free exercise of their religion.”

Note G, [p. 28.]