ON THE LEVEL OF THE BALTIC.

About the middle of the last century, a controversy took place among the natural philosophers of the north of Europe, regarding the alleged gradual lowering of the level of the sea in general, and of the Baltic Sea in particular. Celsius was the first who introduced this idea to notice. He generalised it by applying it to all the planets, and was supported by the authority of the celebrated Linnæus. He soon perceived, however, that the point could never be settled by mere discussion, and that facts alone could lead to any certain result. Observation was therefore had recourse to; and thus the dispute in question had at least one good effect, that of directing to the subject the attention of men of science, whose situation might enable them to mark the variations of level that take place along the coasts of the North Sea. The results of investigations undertaken for this purpose, are now beginning to be collected.

In the course of 1820 and 1821, Mr Bruncrona, assisted by the officers of the Pilotage Establishment, and other qualified persons, undertook the examination of all the authentic measures that had been established upon the west coast of the Baltic, during the last half century. The results of this examination are given in a short memoir, inserted in the Swedish Transactions for 1823. The following table indicates the degree to which the level of the sea has fallen during the last forty years, on the coast of Sweden, at various latitudes. It is proper to remark, that, in some of the places observed, the measures were much older, and in some others much more recent, than the period of forty years. In both these cases, the change of level that must have been effected during this period, has been estimated, by calculating the mean annual depression furnished by the observations.

Latitude.Fall of surface
in forty years.		Latitude.Fall of surface
in forty years.		Latitude.Fall of surface
in forty years.
East Coast.Feet.East Coast.Feet.East Coast.Feet.
63°59′1.5059°17′2.1756°10′0.00
......2.5058441.0056110.00
......0.5058421.0855530.00
61432.5058451.17
61372.8358352.00South-West Coast.
61322.5058280.0755230.00
61452.5058110.8355220.00
60112.335881.0057210.00
59460.1757501.0057531.00
59462.0056410.41

Of the facts collected in the course of this investigation, the following may be mentioned as tending to support the opinion of a fall of level.

1st, It is generally believed among the pilots of the Baltic, that the sea has become shallower along the course which vessels ordinarily follow; but, it is added, that this alteration is more sensible in the places where the tide collects sand, detached pebbles, and sea-weeds, or in those where the bottom is composed of rocks. The same observation has been made in the neighbourhood of some large towns and fisheries; for example, a hydrographic chart made in 1771, gives six fathoms for the mean depth of the sea opposite the harbour of Landskrona, whereas, in 1817, the sounding line scarcely gave five fathoms at the same point.

2d, According to the oldest and most experienced pilots, the straits which separate the numerous islets scattered along the coast of Sweden, from Haarparanda to the frontiers of Norway, received vessels that drew ten feet of water; now they are not practicable for boats that draw more than two or three feet.

3d, The pilots further affirm, that, along the whole coast of Bahusia, the bottom undergoes a diminution, which becomes sensible every ten years in certain places, where it is composed of rocks. Several other parts of the Baltic may be cited, in which a similar change has been remarked.

M. C. P. Hallstrom, in an Appendix to Mr Bruncrona’s Memoir, gives the following table of the diminution observed in the depth of the waters of the Gulf of Bothnia.

Places.Mean marked
in		Height
of the water
reobserved
in		Fall beneath
the original
mark in feet.		Number
of years.		Fall of the
water in 100
years, in feet.
Raholem, parish of Lower Kalix,170017502.05504.10
17752.49754.32
Stor Rebben, parish of Pitea,175117851.70345.00
17961.90454.22
Ratan, parish of Bygdea,174917852.70364.72
17952.50465.43
18192.60703.47
177417850.55115.00
17951.16215.52
18191.60453.57
179518190.65242.71
Rönnskat, on the coast of Wasa,175517971.70424.05
18212.87654.35
Wargön, on the coast of Wasa,175517851.45304.83
17971.69424.02
18212.87654.35
Lögfrundet, near Sefle,173117852.90545.37
17962.17653.34
Ulfon, in Angermanland,179518221.58275.85

It is not demonstrated that the numbers of the last column represent exactly the lowering of the water in a century; for it has not yet been sufficiently determined if this lowering be uniform, or if it vary at different periods, and if it depend upon some local circumstance,—upon the climate,—or upon the state of the atmosphere. Nor is it properly established, that this lowering, which becomes less perceptible from the north of the Baltic, until it disappears entirely at the southern extremity, follows precisely the same law of diminution as the latitude. It appears to be uniform in the whole extent of the Gulf of Bothnia, and it rises about four feet and a quarter in that region; at Calmar (lat. 57° 50′) it is only two feet; but it is not yet known whether it decreases in a regular manner between these two places.

Some authors consider the facts related by MM. Bruncrona and Halstrom, as deciding the question in favour of those who believe in a lowering of the level of the Baltic. The editor of the Annalen der Physik[384] goes farther, and seems to consider it as confirming the opinion of a general lowering of the level of the sea. In support of this opinion, he adduces the traditions and observations of the natives of Otaheite and of the Moluccas and Sunda Islands, regarding the retreat of the sea in several parts of their coast. We are disposed to stand neutral in this matter. The geographers who have collected the greatest number of facts relating to the level of the inland seas, and of the ocean in its various regions, find nearly as many in favour of a rise as in favour of a fall of level. The very distribution of contrary indications, leads them to believe in a partial displacement of the mass of waters from one region towards another, and even from the one side of an inland sea towards the opposite side; a displacement which might be owing to fugitive or more or less durable causes, such as a variation of temperature in the polar regions, the action of winds and of currents, modified by the greater or less quantity of water in the rivers that feed the different basins, upon the sides opposed to their direction.

Are the facts contained in the memoir in question of a nature to overthrow this opinion? They do not appear so to us. The two series of observations which are adduced, only shew a fall upon the coasts of Sweden, properly so called, that is to say, upon the west coast of the Baltic, and the east coast of the Cattegat. Two observations only have been made upon the coasts of Finland, toward the extremity of the Gulf of Bothnia. These facts would perfectly accord with the opinion of those who think that the currents determined from the north to the south of the Baltic by the numerous streams which rush into it, push the waters toward the south shore, that of Pomerania, Mecklenbourg, and Holstein; and that the waters consequently gain upon the land on this coast, as numerous historical facts attest, while they retire along the northern shores, those of the Gulf of Bothnia. Be this as it may, the question as to the constancy of the level of the sea cannot be considered as decided, until a long series of observations shall have been made upon authentic and perfectly fixed measures erected upon all the shores of the different seas, and of the different regions of the ocean. Those which have been published in the Swedish Transactions furnish important documents for this purpose; and similar ones should be begun to be collected in other countries.

The phenomena exhibited by the waters of the Baltic engaged the attention of two rival speculators, Playfair and Deluc; and their views are often alluded to by geologists. We shall here state them in their own words. Professor Playfair, in his well known and elegant work on the Huttonian Theory of the Earth, has the following remarks:

“If we proceed further to the north, to the shores of the Baltic for instance, we have undoubted evidence of a change of level in the same direction as on our own shores. The level of the sea has been represented as lowering at so great a rate as forty inches in a century. Celsius observed, that several rocks which are now above the water, were not long ago sunken rocks, and dangerous to navigators; and he took particular notice of one which, in the year 1680, was on the surface of the water, and, in the year 1731, was 20½ Swedish inches above it. From an inscription near Aspo, in the lake Melar, which communicates with the Baltic, engraved, as is supposed, about five centuries ago, the level of the sea appears to have sunk in that time no less than thirteen Swedish feet. All these facts, with many more which it is unnecessary to enumerate, make the gradual depression, not only of the Baltic, but of the whole Northern Ocean, a matter of certainty.”—Playfair’s Illustrations, p. 445.

That indefatigable and accurate observer De Luc, has the following commentary on the preceding passage.

“It would be unnecessary to mention even the two inconsiderable facts above, if the depression of the level of the seas were indeed a matter of certainty; for the best authenticated and the least equivocal monuments of their change would then abound along all their coasts. But proofs are every where found that such a change is chimerical: they may be seen in all the vales coming down to these seas, in which there is no perceptible impression of the action of any waters but those of the land, and no vestige, through their whole extent, of any permanent abode of those of the sea; and proofs to the same effect are equally visible, along the coasts of both these seas, in all the new lands which have been formed on them, and which, being perfectly horizontal from the point where their formation commenced, evidently show that the water displaced by them has been constantly at the same level. Hence appears the necessity of multiplying, as I have done, and shall continue to do, for the subversion of a prejudice of such ancient date, the examples of these peremptory proofs of its total want of foundation. The rock mentioned by Celsius had probably been observed by him at times when the level of the sea was different; its known differences much exceeding the quantity here specified. As for the inscription near Aspo, in a country abounding with lakes as much as that which I have above described, if we are acquainted with its terms, we should probably find it to be, like many which I have seen in various places along the course of the Oder and the Elbe, the monument of some extraordinary inundation of the land, from the sudden melting of the snows in the mountains, at a time when the water had been prevented from running off by an equally extraordinary rise of the level of the sea; of which the effects on low coasts may extend very far inland.

“By this conclusion, however, from these few facts, contrary to every thing observed on the coasts of this sea, Mr Playfair thinks himself authorised to maintain, that the gradual depression, not only of the Baltic, but of the whole northern ocean, is a matter of certainty; afterwards he examines merely which of these two causes, the subsidence of the sea itself, or the elevation of the land around it, agrees the best with the phenomena; and he decides in favour of the latter, pointing out its accordance with the Huttonian Theory.”

Note L, [p. 119.]