An Account of the Bell Rock Light-House / Including the Details of the Erection and Peculiar Structure of That Edifice; to Which Is Prefixed a Historical View of the Institution and Progress of the Northern Light-Houses

by Robert Stevenson

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.

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.

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.

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.

Depth of Water.

Depth of Water upon the Bell Rock.