[Footnote 201: In the county of Suffolk, near Wood Bridge, at the distance of seven or eight miles from the sea, are the Crag-pits, in which prodigious quantities of sea shells are discovered, many of them perfect and quite solid, (Pennant's Arctic Zoology, Introd. p. 6.) Lincolnshire affords various proofs of the same kind; but some other circumstances in the appearance of that coast, just about to be taken notice of, indicate changes of a more complicated nature.] 391. The shores of the Low Countries, and of Holland, have been often instanced in proof of the same kind of changes, and it has been supposed, that, independently of those artificial barriers which at present exclude the waters of the ocean from overflowing a great part of this tract, nature herself has brought it nearer to the surface than it had formerly been. It is indeed certain, that those countries, to a very great extent inland, have either been under the sea at some period, by no means remote if compared with the great revolutions of the globe, or that they are entirely alluvial, and of the same sort with the Deltas formed at the mouths of rivers. The relative changes, however, of the sea and land on this tract, have been differently represented, and I am unwilling, on that account, to found any argument on them. 392. If we proceed farther 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 this sea has been represented as lowering at so great a rate as 40 inches in a century. Celsius observed, that several rocks which are now above water, were not long ago sunken rocks, and dangerous to navigators; and he particularly took notice of one, which, in the year 1680, was on the surface of the water, and in the year 1791 was 20-1/2 Swedish inches above it. From an inscription near Aspô, 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 13 Swedish feet.[202] 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. [Footnote 202: Frisii Opera, tom. iii. p. 274.]