CHAPTER I.

NAME OF THE ROCK,--SITUATION AND DIMENSIONS,--NATURAL HISTORY,--DEPTH OF WATER, AND CURRENT OF TIDES.

In the Introduction, I have given an account of the institution of the Board of Commissioners of the Northern Light-houses; of the progress made in the erection of Light-houses on the coast of Scotland; the probable future operations of the Board, and the general economy or management of its affairs. I now come to treat in detail of the Bell Rock Light-house, as the chief object of this work; and, in the present chapter, I propose to give the general history, and a description of this dangerous Rock.

_Name of the Rock._

[Sidenote: Name.]

[Sidenote: Origin of the Name.]

There is perhaps nothing in history more arbitrary, or difficult to account for, than the origin of proper names, nor, in general, any research more unsatisfactory, than a prolix inquiry into their etymology. The charts of the nautical surveyor are the proper records for the names of places upon the sea-coast; but such maps are comparatively of late invention. The first sea-chart which we hear of in England, was that brought from Spain in 1489, by Bartholomew Columbus, to illustrate his brother’s theory of the discovery of America; and the earliest, applicable to the coast of Scotland, is the chart of the voyage of James V., from the Firth of Forth, by the Orkney and Western Islands, to the Firth of Clyde and coast of Galloway, in the year 1540. This map was published at Paris by Nicolay D’Arfiville, Seigneur Du d’Aulphinois, &c. chief Cosmographer to the King of France, in 1583; and afterwards in Edinburgh, in the year 1688, by John Adair, F. R. S., Geographer for Scotland.

[Sidenote: Inch Cape.]

The French writer gives a hydrographical description of the coast of Scotland, in relation to the Royal voyage, from Leith to the Solway Firth , noticing the distances of places, the tides, and the rocks and sand-banks, or “_dangers_,” as they are more generally termed, which it was necessary to avoid. In adverting to the course from Leith by the east coast to Duncansby-Head, in Caithness, he observes, “Entre Finismes [Fifeness] et la pointe nommé Redde, xii mille à l’est sud-est du costé de la dicte pointe Redde, gist un danger appelé _Inchkope_.” This is unquestionably the Bell Rock, the inch or island of the _Cape_, and with a reference to the Redhead, to the north of Aberbrothock, the highest and most remarkable point on that coast. In Adair’s collection of nautical charts, and descriptive account of the eastern coast of Scotland, published in 1703, the Bell Rock is indifferently termed _Scape_ and _Cape_; and the fishermen on the shores of Angus uniformly call it the _Cape Rock_. In some old charts, particularly by the Dutch, whose name for a headland is _kappe_, it is also called _skape_ and _scaup_. It does not, however, seem that any inference can be drawn from these various appellations; and, although it were to be conjectured, that the Inch Cape was, at a very remote period, permanently above water, and in all respects an island, the most rational hypothesis would still remain, and be indeed confirmed, that this name was given it on account of the relation it bore, especially in situation, to the cape of Redhead.

[Sidenote: Bell Rock.]

It is perhaps more difficult to assign the true origin for the modern term of _Bell Rock_, by which this dangerous reef is now universally known. There is a tradition, that an Abbot of Aberbrothock directed a bell to be erected on the Rock, so connected with a floating apparatus, that the winds and sea acted upon it, and tolled the bell, thus giving warning to the mariner of his approaching danger. Upon similar authority, the bell, it is said, was afterwards carried off by pirates, and the humane intentions of the Abbot thus frustrated. This story has, by a modern poet, been made the subject of the ballad of “Sir Ralf the Rover,” which, for the reader’s amusement, is inserted in the Appendix, No. II.

[Sidenote: Erection of a Bell.]

Of the erection of the Bell, and of the machinery by which it was rung, if such ever existed, it would have been interesting to have had some authentic evidence. But, though a search has been made in the chartularies of the Abbey of Aberbrothock, preserved in the Advocates’ Library, and containing a variety of grants and other deeds, from the middle of the 13th to the end of the 15th century, no trace is to be found of the Bell Rock, or any thing connected with it. The erection of the bell is not, however, an improbable conjecture; and we can more readily suppose that an attempt of that kind was made, than that it had been intentionally removed, which in no measure accords with the respect and veneration entertained by seamen of all classes for land-marks; more especially, as there seems to be no difficulty in accounting for the disappearance of such an apparatus unprotected, as it must have been, from the raging element of the sea. It is not therefore unlikely, that the popular appellation by which this Rock has more recently been known, may owe its origin to the tradition of the Abbot’s humanity and public spirit; and when we consider that the churchmen of those days were well acquainted with the history of the celebrated Pharos of Alexandria, and may have heard of the fire-towers and sea-marks, which Mr Bryant, in his Mythology, conjectures existed in very remote times, it is natural to suppose, that these learned persons had, at a pretty early period, turned their attention to the subject, and had attempted, in the mode which has been figured, to point out and guard against the danger.

Amidst these speculations, it must not, however, be overlooked, that this Rock may have acquired its present name from its shape or figure; for at the commencement of the author’s operations, he remarked, that the site of the light-house, at some distance, had much the appearance of a large bell; and although this part was not more than four feet above the general level of the Rock, yet by supposing it to have been the nucleus of a larger mass, in the central part of the Rock, gradually wasted away by the washing of the sea, it may at a former period, from that resemblance, have obtained the appellation it now retains.

_Situation and Dimensions._

[Sidenote: Situation.]

The Bell Rock may be described as a most dangerous sunken reef, situate on the northern side of the entrance of the great estuary or arm of the sea called the Firth of Forth; and as such directly affecting the safety of all vessels entering the Firth of Tay. Its position, as will be seen from the Charts, Nos. 3. and 4., which accompany this work, is in west longitude from Greenwich 2° 22´, and in north latitude 56° 29´. From St Abb’s Head in Berwickshire, it bears north by east per compass, (variation 27° 20´ west in the year 1819), and is distant about 30 miles; from the Island of May north-east 17 miles; and from the promontory or cape called the Redhead, in Forfarshire, it bears south-west, and is distant 14 miles. But in easterly directions no land intervenes between the Bell Rock and the coasts of Norway, Denmark, Germany and Holland.

[Sidenote: Dimensions.]

The dimensions of the north-eastern or higher compartment of the Rock where the light-house is built, are about 427 feet in length, and 230 feet in breadth. Besides these dimensions, the south-western reef extends about 1000 feet from the main rock. The greatest length, therefore, of the Bell Rock, which may be said to be dangerous to shipping, is about 1427 feet, and its greatest breadth is about 300 feet; but the outline or margin of the Rock is quite irregular, as will be seen from the Plates marked Nos. 5. and 6.

_Natural History._

[Sidenote: Mineralogy.]

The Bell Rock consists of sandstone of a reddish colour, which in some places contains whitish and greenish spots of circular and oval forms, irregularly interspersed through the rock. It is of a fine granular texture, containing minute specks of mica. It is very hard, and, in the language of the artificer, is tough, and rather difficult to work; and in some parts it is found to rise in masses having a conchoidal fracture. Its angle of inclination with the horizon is about 15 degrees, dipping towards the south-east. The strata are thick and unequal, strongly cemented together, and running in the direction of north-east and south-west. The surface of the Rock is rugged, and full of cavities, so that walking upon it becomes rather difficult. A longitudinal section of the Bell Rock, taken in a north-easterly and south-westerly direction, may be described as consisting of a higher and a lower level. The cross section, taken in a south-easterly and north-westerly direction, exhibits the abrupt and pointed terminations of the strata, though it appears level when seen from a distance.

[Sidenote: Wasting effects of the Sea.]

[Sidenote: Natural History.]

It would be a speculation highly interesting to the geologist, to inquire into the probable early history of the Bell Rock, and the changes produced on it by the wasting effects of the waters of the ocean. When we consider the similarity of the red sandstone of this rock with the Redhead of Forfarshire, and opposite shores of Berwick in the neighbourhood of Dunglass, and take into view that there is a ridge or shallower part of the bottom, which extends a considerable way from the Bell Rock in the direction of these shores, we may infer, that the Rock itself had extended at one time much further. We are also enabled to trace the same formation, penetrating to the northward through Ross-shire, and quite across the kingdom, in a southern direction, to Cumberland. At a period indefinitely remote in the history of the globe, we may therefore imagine that one continuous bed of red sandstone had stretched across the Firth , forming a barrier by which the great collection of waters of the Forth and Tay have been pent up.

[Sidenote: Proofs of the Sea having occupied a higher level.]

In support of this opinion, we have the most unequivocal proofs of the waters of those friths having formerly occupied a much higher level. Of these we may notice the general appearance of their water-worn shores, and a bed of oyster-shells near Borrowstounness, which has been traced to the extent of three miles in length, and about two fathoms in thickness, lying in their natural state, but now upwards of 35 feet above the present level of the sea. Under these circumstances, and many others which might be adduced, it is not improbable that the Bell Rock has at one time been connected with the opposite coasts; and when we consider the general waste of the land, which is apparent in all directions from the impulse of the sea, it may at least be concluded, that at no very remote period, the Rock has been of much greater superficial extent, and above the level of the highest tides. Nor need we be surprised that such changes upon this remote and insulated spot should have been lost sight of, owing to their gradual and almost imperceptible effects, compared with the short period of the life of man, and in absence of all testimony excepting that which is oral.

[Sidenote: Plants.]

With regard to the marine Plants which grow upon the Bell Rock, we may observe that the lower parts of it are covered with the stronger or larger sorts, as the great tangle, _Fucus digitatus_, the roots of which rarely appear above the water, while it is seen at the depth of several fathoms, growing with the greatest luxuriance, and has often been observed by the author from a boat in fine weather, as a means for ascertaining, by the direction of the leaf, the changes of the currents of the tide at the bottom. The Badderlock, or Henware, _Fucus esculentus_, is found only on the north-eastern and south-eastern extremities of the Rock, growing at low water-mark of spring-tides, and seems to prefer the most rapid currents of the sea, and places where the heaviest breach takes place. In such situations it grows in great abundance at the Bell Rock, where it has been measured of the length of eighteen feet, and of proportionally increased breadth. Perhaps some of these plants are of considerable age; but at the works of the Carr Rock Beacon, off Fifeness, it was found that the growth of the badderlock was so very rapid, that the plant attained to the length of seven feet upon the new building, in the course of the winter and spring months. The higher parts of the Bell Rock abound with the smaller fuci, as _Fucus mamillosus_, and _F. palmatus_, or common dulse. _F. lycopodiodes_, _alatus_, and _coccineus_, are found on the older stalks of the great tangle, and _F. subfuscus_ and _confervoides_ occupy the smaller pools. In some places, the rocks are rendered slippery with _Ulva compressa_ and _umbilicalis_; and the higher parts of the Rock, and the basement or lower courses of the light-house, are so covered with _Conferva rupestris_, as to produce the appearance of a sward of grass.

[Sidenote: Animals.]

Of the feathered tribe of animals at the Bell Rock, we notice the shag, cormorant, and herring-gull, which sometimes rest upon the Rock when in search of codlings and other small fishes. It also formed the resting-place of numerous seals at the commencement of the operations of the Light-house, but these amphibious animals, as well as the birds, have now almost entirely left it. The common crab and lobster are sometimes found here in the crevices of the rock. The _Lepas balanoides_, or acorn-shell, the common limpet, mussels of a small size, and the white _buckey_ or _Buccinum lapillus_, abound on the rock. The _Actinia crassicornis_, _Asterias glacialis_ and _oculata_, are common. A minute crustaceous insect, called, by Dr Leach, _Limnoria terebrans_ (_Lin. Trans_, vol. XI. p. 371.), appeared in great numbers in the submersed wood work of the temporary erections on the Rock.

[Sidenote: Insect destructive to Timber.]

So destructive to timber is this small insect, that the Norway logs, laid down to support the temporary railways in 1807, when lifted in 1811, were found to have been reduced by its ravages from 10 inches square to 7 inches, or at the rate of about an inch in the year. The author having had occasion afterwards to examine the timber-bridge of Montrose, found the attacks of this insect upon the wooden piers to be so alarming as to endanger that fabric; and after many trials for the preservation of timber in such situations, the Trustees were ultimately induced to cover the upright beams with sheet-copper. Upon another occasion, when the author was called to inspect the Crinan Canal, he found the gates of the sea-locks so destroyed, chiefly by this little animal, that the locks lost seven feet of their depth of water in the course of the night. It is further remarked, that the deserted cavities, formed by the perforations of the Limnoria, frequently become the residence of larger marine insects, belonging to the Linnæan genus Oniscus.

[Sidenote: Experiments with pieces of timber trenailed to the Rock.]

In the year 1814, with a view to experiment on the effects of these destructive vermes, I fixed down specimens of teak-wood, oak, black birch, Memel and Norway fir timber, on the Bell Rock. The only specimen which remained imperforate till 1820, was the teak-wood. The rest were almost entirely destroyed in the course of two or three years. This may be regarded as a matter of some importance, in a national point of view, in directing the employment of teak-wood for the sea-lock gates of canals and for ship-timbers. From the excellency of the situation of the Bell Rock for such experiments, I have caused another set of timbers to be trenailed to the rock, in a situation where, like the former, they are occasionally uncovered by the water. These last pieces of timber were laid down in the month of October 1821. They are eighteen in number, each measuring 5 inches square, and 30 inches in length; and are of the following kinds, viz. British and American oaks and firs, Memel fir, Scotch elm, beech, sycamore, larch, teak-wood, mahogany, bullet-tree, locust-wood, and blue gum-wood from Van Dieman’s Land.

[Sidenote: Attempt to plant Muscles on the Rock.]

When the workmen first landed upon the Bell Rock, limpets of a very large size were common, but were soon picked up for bait. As the limpets disappeared, we endeavoured to plant a colony of muscles, from beds at the mouth of the river Eden, of a larger kind than those which seem to be natural to the rock. These larger muscles were likely to have been useful to the workmen, and might have been especially so to the light-keepers, the future inhabitants of the rock, to whom that delicate fish would have afforded a fresh meal, as well as a better bait than the limpet; but the muscles were soon observed to open and die in great numbers. For some time this was ascribed to the effects of the violent surge of the sea, but the _Buccinum lapillus_ having greatly increased, it was ascertained that it had proved a successful enemy to the muscle. The _buccinum_ being furnished with a proboscis capable of boring, was observed to perforate a small hole in the shell, and thus to suck out the finer parts of the body of the muscle; the valves of course opened, and the remainder of the fish was washed away by the sea. The perforated hole is generally upon the thinnest part of the shell, and is perfectly circular, of a _champhered_ form, being wider towards the outward side, and so perfectly smooth and regular, as to have all the appearance of the most beautiful work of an expert artist. It became a matter extremely desirable to preserve the muscle, and it seemed practicable to extirpate the _buccinum_. But after we had picked up and destroyed many barrels of them, their extirpation was at length given up as a hopeless task. The muscles were thus abandoned as their prey: and in the course of the third year’s operations, so successful had the ravages of the _buccinum_ been, that not a single muscle of a large size was to be found upon the rock; and even the small kind which breed there, are now chiefly confined to the extreme points of the rock, where it would seem their enemy cannot so easily follow them.

[Sidenote: Habits of Fishes.]

In speaking of the habits of fishes, it deserves notice that they have their particular grounds and shores which they frequent; for while the vessels attending the works at the Bell Rock were stationed there, different kinds of fish were caught as the depth and bottom varied. About high-water, and especially during ebb-tide, when the sea is smooth on the rock, the _Podley_ (chiefly the fry of the coal-fish, but including also the young of the _Gadus virens_) is so numerous, as almost entirely to cover it from view. Near the rock, the small red cod is often found in abundance: at some distance, as the bottom, which is covered with marine plants near the rock, alters to coral, gravel, shell sand, fine sand and mud, all of which occur in a range of depths from 4 to 23 fathoms towards the north, different kinds of fish are found; first, the codling, which ceases to be wholly red, but becomes only speckled with reddish spots; then, upon the finer or mud grounds in the track of the tides of the Firth of Tay, whiting, haddock, flounder, and occasionally the sole. On the southern side of the rock, where the water deepens to 35 fathoms, the large white cod, in company with ling, conger-eel, halibut, skate, thornback, plaise, turbot, wolf-fish and large coal-fish are found. The dog-fish appears to be very general, and seems to prey chiefly upon the haddock and cod. The mackerel and gurnard are found together near the surface, and do not seem to be confined to particular grounds, but occur wherever the water is of a considerable depth. Herrings are found in the bays of the opposite shores in great abundance at the fishing season, when they are understood to be migrating towards the south. It has often been observed, in the course of the Bell Rock operations, that, during the cold weather of spring and autumn, and even at all seasons, in stormy weather, when the sea is much agitated by wind, the fishes disappear entirely from the vicinity of the rock, probably retreating into much deeper water, from which they do not seem to return, until a change of weather has taken place; so much was this attended to by the seamen employed on this service, that they frequently prognosticated and judged of the weather from this habit of the fishes, as well as from the appearances of the sky.

_Depth of Water._

[Sidenote: Depth of Water.]

[Sidenote: Depth of Water upon the Bell Rock.]

At the time of high-water of spring-tides, the south-western reef is about 16 feet, or nearly the whole rise of the tide, under the surface of the water; while the part of the rock on which the light-house is built, is about 12 feet below high water-mark of spring-tides: At low-water of neap-tides, hardly any part of the rock is visible: But at low-water of spring-tides, the _general level_ of the north-eastern end where the light-house is built, is about four feet perpendicular above the level of the sea, though particular points measure six or even seven feet in height above the low-water mark of spring-tides.

[Sidenote: Depth at the distance of 100 yards, and upwards from it.]

At the distance of about 100 yards from the rock in all directions, excepting on the south-western reef, there is a depth of water varying from two to three fathoms at low water of spring tides. On the north-west side, or in the direction of the shores of Forfar and Fife, the greatest depth is 23 fathoms; but on the south-eastern or seaward side, in the direction of the _dip_ or inclination of the strata, the water deepens more suddenly to 35 fathoms; in the same direction from the rock, however, the soundings again become less, being only 22 fathoms upon Mars Bank, distant about 33 miles; this bank appears to be a deposition formed by the joint operation of the waters of the Friths of Forth and Tay, influenced by the great tidal wave of the German Ocean. It may here be noticed as a fact connected with the depth of the German Ocean, that at Queensferry passage, in the Firth of Forth, the depth of the water is about 35 fathoms, while the greatest depth of the sea across to Denmark, does not exceed 45 fathoms. The depths of the German Ocean will be seen, by inspecting Chart No. 3., where sectional lines are delineated between various points of Great Britain and the opposite Continent, on which the reader will see the relative depths marked by shaded lines, in a new and it is hoped a perspicuous manner.

_Current of the Tides._

[Sidenote: Currents of the Tide.]

[Sidenote: Tides at the Bell Rock.]

The tides at the Bell Rock, are observed to follow the same laws as on the opposite shores of the Firth of Forth. The currents along the coast take their direction from the figure of the land, and, in their course, they are therefore occasionally deflected from, and inclined towards it. At the Bell Rock the flood-tide sets south-west, and the ebb-tide north-east, being nearly in the direction of the shores of Forfar and Kincardine. The velocity of the water in spring-tides, or when the sun and moon are in conjunction, and in opposition, is about three miles _per_ hour, but in neap-tides, or at the quadratures of the moon, the current is only at the rate of about one mile _per_ hour. On the days of new and full moon it is high-water _upon_ the Bell Rock at half past one o’clock, being about the same periodic time as at the harbour of Arbroath, or nearest point of the mainland. In the ordinary state of the weather, the perpendicular rise and fall of the sea at the Bell Rock, in spring-tides, is 15 feet, and in neap-tides, 8 feet; but so much depends upon the direction of a prevailing tract of winds, that the tides are often found to vary from 1 to 3 feet above and below these numbers. This irregularity in the tides of the German Ocean and its subsidiary friths or inland seas will be easily accounted for, by considering the effect of westerly winds passing for a length of time over the Atlantic, which must naturally force an undue quantity of water from thence into the entrance of the North Sea, between the coasts of Scotland and Norway; while the Strait of Dover, to the southward, from the same cause, is gorged by the surplus waters of the British Channel flowing in an opposite direction, and checking the tide of the German Ocean. When the winds blow from southerly and easterly directions, the reverse of this happens, and the waters are then proportionally low.

[Sidenote: In and Off shore Currents.]

A curious anomaly connected with the flowing and ebbing of the sea, in the early part of each tide, is observable in the contrary currents which take place along the shore, and at a distance from it. For example, the flood-tide begins to flow in many situations two or even three hours sooner on the shore than at the distance of from one mile to four miles in the offing. The same thing also happens with regard to the ebb-tide, which begins to fall and run in a contrary direction to the flood-tide, two or three hours sooner on the shore than at a distance. These effects are very different from the state of things three or four leagues from the land, or in the open sea, where the lateral motion of the tide-waters is scarcely sensible. That an extensive tract of coast should produce changes on the current of the tides, is perhaps what we should expect; but it is somewhat curious to find the same appearances connected with small islets, and, as in the case of the Bell Rock, even with an insulated reef, situate at the distance of 12 miles from the land, and sunk to the depth of from 2 to 3 fathoms under the surface of high-water. So strikingly observable is this, that the tide begins to ebb about two hours sooner on the Bell Rock than at the short distance of one mile from it. In the course of the light-house operations this was rendered sufficiently obvious, by the swinging round of the several vessels at their moorings according to the flood and ebb tides. For example, the Floating Light-ship was moored about three miles in a north-west direction from the Bell Rock, and the moorings of the Tender and two Stone Lighters, were respectively laid down at the distance of ¾ and ½ mile from it, as will be seen from Plate V. Now, these vessels were all found to swing to the tide at periods proportional to their distance from the rock. Although it may, therefore, seem strange, that this comparatively small object should affect the tides in its vicinity in a manner similar to the shores of an extensive coast; yet, as the rock shelves outwards, with an extensive base, especially on the northern side, it must impede the under current of the tide, and indeed forcibly proves the existence of such under currents.

[Sidenote: Not accounted for by Writers on the subject.]

To account for these in and off shore tides, or central and marginal streams, would be interesting. But to what cause shall we ascribe them? Sir Isaac Newton, and the other eminent philosophers who have followed that great man in considering the theory of the tides, confine their attention chiefly to an explanation of the influences of the sun and moon, and the laws of gravitation, in affecting the waters of the ocean, leaving it to the result of experience and observation to account for such anomalies as those to which we now allude. It is noticed by Adair, Mackenzie, and other nautical surveyors, that the tides run longer upon the shore than in the offing, and the advantage of working a ship with _in and off shore tides_, is familiar to every mariner. The existence of these opposite currents was also known to the author, prior to the commencement of the Bell Rock works, but they had not struck him so forcibly till that period. For here, even after the flood-tide had overflowed the rock, and put a stop to the operations, the boats in carrying the artificers on board of the Tender, had still to row against the current of a strong ebb-tide.

[Sidenote: Currents along Shore considered as Eddy-tides.]

It would be foreign to this work to enter into the theory of the tides generally; all, therefore, that is here proposed, is to endeavour to account for these in and off shore currents. In doing this, however, it will be necessary to observe, that the _great wave_ or “theoretical tide,” as it has been termed by the late eminent Professor Robison, is produced by the united attraction of the sun and moon, which, between the Tropics, has been calculated by philosophers to raise the water from 8 to 14 feet perpendicularly. It is observable, that the attractions of these heavenly bodies elevate the parts of the ocean to which they are vertical, without having any direct tendency to progressive or lateral motion. The currents along our coasts, may therefore be considered merely as Eddy-tides, occasioned by the interposition of the land, which obstructs the undulating motion incident to the rise or fall of a fluid. In this manner the land may be said to displace a portion of the tidal waters which have been elevated above the medium level of the sea; and were it not for such obstruction, the great waves of the tide might be supposed to undulate indefinitely over the expanse of the ocean. To compare small things with great, these effects may be conceived as in some degree exemplified, by the disturbing effect of a vessel passing along a navigable canal, or the undulations which are observable in the _wake_ of a ship or wheels of a steam-boat in motion on a smooth sea.

[Sidenote: Progress of the Great Waves of the Tides.]

The great wave which supplies the _British tides_, appears to be propagated between the coast of Labrador and Greenland, on the one hand, and the European shores on the other; and this great wave seems to be divided into two lesser waves. One of these flows between Ireland and the coast of France, into the British and St George’s Channels; while the other enters by the North Sea into the German Ocean; and in its course from north to south, supplies all the friths, rivers, and bays connected with it, invariably in the form of _In and Off shore tides_, which are every where observable along the margin of this great basin. This northern wave is found to occupy about 12 hours in flowing southward from the 58th to the 52d degree of latitude, or from the Orkney Islands to the numerous Sand-banks which pervade and encumber the apex of the German Ocean, where the currents become extremely desultory and irregular. The coast of the British Isles, accordingly, may be said to, displace a portion of this northern wave, and thus to produce the irregularities which we are endeavouring to account for.

[Sidenote: Progressive periods of High-Water in the Firth of Forth.]

At present, we shall confine our attention to the tides of the Firth of Forth. Here, as on other parts of the coast, the tidal waters have a tendency to flow towards the shores and higher parts of the Forth, till the instant of high-water upon the shore, when the tide begins to ebb, and run in a contrary direction. A central stream, however, continues to run with unabated force, as flood-tide, during two or even three hours longer, as before noticed, according to the situation and local circumstances of the coast. It appears, from a comparison of the several periods of high-water on the shores of the Firth of Forth, as nearly as some of them could be ascertained, that the precise time of high-water becomes later and later in the same tide, as we proceed westward; at the Bell Rock, for example, it is high-water on the days of new and full moon, as before noticed, at ½ past 1 o’clock; at the Carr Rock, at ¾ past 1; at Elie, still further up the Firth , at 2; Kinghornness, at ¼ past 2; Queensferry, at ¾ past 2; and at Alloa, at ¾ past 3 o’clock. The off-shore stream of the tide continues to flow proportionally longer till it has supplied the higher parts of this estuary with its portion of tidal waters; and in like manner, the central stream of ebb-tide continues its course till these waters are again run off.

[Sidenote: Currents at the Mouth of the Dee and other Rivers.]

In many points, it is found, that the operation of the tidal waters of extensive arms of the sea, bears a close resemblance to what is observable upon the small scale in the currents of rivers, especially at their junction with the ocean. An interesting example of this occurs on the river Dee, which falls rapidly into the harbour of Aberdeen. Here the author having occasion to make some observations on the tides in the summer of 1812, stationed several assistants at low-water mark, between the entrance of the harbour and the bridge, about two miles up the river. The waters of the Dee, even at the entrance of the harbour, have almost a constant current seaward, notwithstanding the opposite direction of the flood-tide of the Ocean. On the occasion alluded to, one of his assistants, a very intelligent shipmaster, continued at his post while the water flowed up to his middle; and, when accosted about his situation, he significantly observed, “That it was rather extraordinary, as the stream had never ceased to indicate the continuance of an ebb-tide, while the water was still rising upon his body.”

[Sidenote: Water salt at bottom and fresh at top.]

In connection with these observations on the tides, some experiments were also made with an instrument adapted for lifting water from considerable depths, without the possibility of its intermingling with the surface water. By means of this instrument, the water at the bottom of the Dee, at Aberdeen, was found to be salt, while that at the surface was quite fresh. These streams of fresh and salt water run in distinct currents, and in contrary directions, the salt water, from its greater specific gravity, flowing at the bottom of the river, and fluctuating with the level of the ocean, while the fresh water is actually lifted upwards, and continues all the while to flow seaward on the surface of the salt water. Towards the point of high-water, however, the flood-tide gains strength on the margin of the basin of the harbour, where the water becomes salt, and forms an eddy-tide in a contrary direction to the central stream, which is observed still to run toward the sea. Having made similar observations on the waters of the Thames, the Garonne, and other rivers, with nearly the same results, after making allowance for the more level state of the country, in the track of these great streams,--it is concluded, that the currents at the embouchure of rivers bear a strong resemblance to the operation of the in and off shore tides of the ocean.

[Sidenote: Phenomena of in and off shore Tides accounted for.]

We further observe, that the great wave of the German Ocean produces its tides in regular succession, and at stated periods, as it moves from north to south; but the tides of the more inland seas are subject to many irregularities, both in their periodic times, and in the direction of their currents. Let us suppose, then, that we have arrived at the instant of high-water on the shores at the entrance of the Firth of Forth, and that the tidal waters are then moving in a body, and with a certain pressure, towards the higher parts of the Firth , and even affecting the river above the bridge of Stirling. We find, that at the entrance of this estuary, on the days of new and full moon, it is high-water at a quarter past one o’clock; but at Alloa, situate 70 miles above the Bell Rock, it is not high-water till about two hours and a half later. The in-shore tidal waters having to encounter the shelving shores, islands, sunken rocks, and projecting points of land, which lie in their course up the Firth , acquire lateral as well as perpendicular motion, and being thus checked in their progress, are brought sooner to a maximum state than the off-shore stream, which flows in deeper water, and comparatively free of obstruction, till it reaches its ultimate limits; though it gradually diminishes in breadth, till the stream of the _new tide_ gaining strength becomes general; and the central current, formerly running in a contrary direction, at length disappears, and takes the course of the new tide.

We would, therefore, be understood to ascribe this anomaly in the flowing and ebbing of the sea, to the obstruction which the current of its waters meets not only at the surface or margin, but at the bottom, which, from the variety of the soundings of the depths, appears to be as various as the face of the land. A striking proof of this is afforded at the Bell Rock: on the northern side of which there are 11 fathoms, at the distance of about three quarters of a mile; while, on the southern side, and at a similar distance, the water deepens to 35 fathoms; so that a perpendicular section of this rock under water forms a precipitous declivity, such as we are quite accustomed to see on the land. Now, if we apply this irregular conformation of the bottom of the sea, to the production of the in and off shore tides, and conceive that the tidal currents extend their motion to the bottom, it must be evident, that this obstruction presented to the stream will bring the tides to a maximum state sooner on the northern side of the rock, where the water is so much shallower, than on the southern side. This is also agreeable to observation; for, the tides _upon the Bell Rock_ begin to flow and ebb one hour sooner than at the distance of about three quarters of a mile from it on the northern side, and about two hours and a half sooner than at the same distance on the southern side. The marginal current is thus checked by the shallowness of the water, and the projecting points of land; while the central stream, flowing comparatively without obstruction, continues to run till the most inland creeks are supplied with tidal water; and _vice versâ_, it continues its stream outwards, till these waters are again run off.

[Sidenote: Progressive times of high-water.]

The progressive times of high-water, at intermediate points between the Bell Rock and the port of Alloa in the Firth of Forth, appear to follow the same general law, as the great wave of the German Ocean in its progress from the Orkneys southward. These observations on the tides of the Forth apply equally to the Firth and River of Tay, and indeed to all the tributary streams and arms of the sea which communicate with the German Ocean, according to their local situations and magnitudes.

[Sidenote: Tides of the Mediterranean and Baltic Seas.]

If due allowance be made for the peculiar situation and circumstances of the Mediterranean and Baltic seas, it is apprehended, from all that we have been able to learn of the operation of the currents at the Strait of Gibraltar, and Sound of the Cattigate, that these seas are supplied and discharged by in and off shore tides or currents, under certain modifications, and making due allowance for local circumstances, in the same manner as on all other parts of the coast.

I have been thus particular relative to the in-shore and off-shore tides, because they appear in a very puzzling form to the mariner, while writers on the theory of the tides are almost silent on this subject.