differs from the Bell Rock, was found from first to last to occasion much inconvenience. The sandstone of the Bell Rock is worn into rugged inequalities. The action of the sea on the igneous formation of Skerryvore has given it the appearance and the smoothness of a mass of dark-colored glass, which made the foreman of the masons compare the operation of landing on it to that of climbing up the neck of a bottle. When we consider how often, by how many persons, and under what circumstances of swell and motion this operation was repeated, we must look upon this feature of the

A choice remained to be made between at least four different curves, which would each comply with the conditions specified in Mr. Stevenson's conclusion-the logarithmic, the parabola, the conchoid, and the hyperbola. The logarithmic, though not unfavorable to the condition of vertical pressure, was dismissed as clumsy; the parabola displeased the eye from its too rapid change near the base; the similarity between the conchoid and the hyperbola left little to choose between them, but the latter obtained the preference. The shaft of the Skerryvore pillar, accordingly, is a solid generated by the revolution of a rectangular hy-spot as an obstacle of no slight amount. perbola about its asymptote as a vertical axis. Its The 7th of August, 1838, is noted as the first exact height is 120-25 feet; its diameter at the day of entire work on the rock. It consisted in base 42 feet, and at the top 16 feet. (p. 61.) The preparations for the temporary barrack, which in first 26 feet from the base are solid, and this por- this case, as in that of the Bell Rock, was contion weighs near 2000 tons. The walls, as they sidered a necessary preliminary, and was in most spring from the solid, are nine feet thick, and respects a copy of its predecessor. Little more gradually diminish to two. Mr. A. Stevenson than the pyramidal pedestal of beams for this considered himself safe in dispensing generally building could be accomplished before the 11th of with the system of dovetailing, which had been September-the last day of work for that season adopted throughout the building in the two pre--and this commencement was swept away in the ceding instances. By an improved construction night of the 12th of November:—a calamity of the floors of the chambers he also supplied the place of the metal chains which Smeaton had used to restrain any disposition to outward thrust in the circle of masonry, and the copper rings by which the cornice of the Bell Rock building is strengthened. The above are some of the principal features of the differences suggested by study and experience between the three works. We must refer our readers to p. 63 for a diagram which makes them sensible to the eye. The following table, however, may be sufficient :

[blocks in formation]

which mortified those whom it could not daunt nor discourage, and which only led to various improved devices for reconstruction. The quarries meanwhile had been busy in Tyree, but the experience obtained during this winter, 1838 and 1839, of the gneiss-rock of that island led Mr. Stevenson to resort for further supply to the granitequarries of Mull. In specific gravity the gneiss has a trifling advantage, but it is less fissile and far more uncertain in quality. Of the quantity hitherto obtained in Tyree not more than one tenth was found fit to be dressed as blocks for the tower.

The next important operation was that of excavating the foundation. This occupied the whole of the working season of 1839, from the 6th of May to the 3rd of September. The gneiss held out stoutly against iron and gunpowder, and Mr. Stevenson calculates the labor at four times that which granite would have required. In the case of the Eddystone, Smeaton was compelled to follow the shape of the rock, and to adapt his lower courses of masonry to a sort of staircase of successive terraces carefully shaped for the adjustment. The formation of Skerryvore enabled Mr. Stevenson to avoid this delicate and expensive process, and to mark out a foundation-pit of 42 feet diameter, the largest he could obtain at one level throughout. This basin, however, required for its

Those who have perused the "Diary" of Mr. R. Stevenson's voyages to and fro, and long residences in anchored vessels at the Bell Rock, will anticipate that much of the difficulty with which the father had to contend was obviated in the case of the son by the application of steam-power to navigation. The first year's operations at Skerryvore were, however, not assisted by this new aux-excavation the labor of 20 men for 217 days, the iliary. A steamer was advertised for, but the river and harbor craft offered for sale were quite unfit to encounter the seas of Tyree, and it was found necessary to build a vessel for such rough service, of 150 tons, with two engines of 30-horse power each. Mr. Stevenson found, as he conceives, compensation for the delay in the accurate knowledge of the reef and surrounding waters which constant trips in the Pharos sailing-vessel of 36 tons procured for him.

firing of 296 shots, and the removal into deep water of 2000 tons of material. The blasting, from the absence of all cover, and the impossibility of retiring to a distance further in any case than 30 feet, and often reduced to 12, demanded all possible carefulness. The only precautions available were a skilful apportionment of the charge and the covering the mines with mats and coarse netting made of old rope. Every charge was fired by or with the assistance of the architect in person, and

One peculiarity of the Skerryvore, in which it no mischief occurred. The operations of 1840 in

cluded the reconstruction of the barrack, in which, though rather more pervious to wind and spray than what Mr. Robins in his boldest mood would have ventured to designate a "desirable marine villa," the architect and his party were content to take up their quarters on the 14th of May. "Here," says the gallant chief,

during the first month we suffered much from the flooding of our apartments with water, &c. On one occasion also we were fourteen days without communication with the shore or the steamer, and during the greater part of that time we saw nothing but white fields of foam as far as the eye could reach, and heard nothing but the whistling of the wind and the thunder of the waves, which was at times so loud as to make it almost impossible to hear any one speak. Such a scene, with the ruins of the former barrack not twenty yards from us, was calculated to inspire the most desponding anticipations: and I well remember the undefined sense of dread that flashed on my mind, on being awakened one night by a heavy sea which struck the barrack, and made my cot swing inwards from the wall, and was immediately followed by a cry of terror from the men in the apartment above me, most of whom, startled by the sound and the tremor, sprang from their berths to the floor, impressed with the idea that the whole fabric had been washed into the sea. p. 152.

This spell of bad weather, though in summer, well nigh outlasted their provisions; and when at length they were able to make the signal that a landing would be practicable, scarcely twenty-four

hours' stock remained on the rock.

As yet nothing of weight but iron and timber had been landed. The first trial of the landing of heavy stones from the lighters, on the 20th of June was a nervous one. It succeeded, but difficulty and hazard in this operation were of constant recurrence; and, as the loss of one dressed stone would frequently have delayed the whole progress of the building, the anxiety was incessant. Eight hundred tons of dressed stone were, however, deposited on the rock this season without damage. On the 7th of July the ceremony of laying the foundation stone was performed by the Duke of Argyll, attended by a party of relations, including the Duchess and Lady Emma Campbell, and many


The summer of 1840 was a stormy one, and it required some habit to contemplate calmly, even from the height of thirty feet, the approach of the Atlantic wave. The exhibition of its power was more formidable during that period of ground swell which follows a protracted gale than amidst the violence of the actual storm. Cool and careful

observation led Mr. Stevenson to conclude that the height of an unbroken wave in these seas does not exceed fifteen feet from the hollow to the crest; but this was magnified to thirty or forty in the estimation of less scientific watchers-some of whom could scarcely familiarize themselves even by repeated experiences of safety to the illusive appearance of imminent destruction. The greatest trial of such a residence was doubtless the occasional inaction resulting from the violence of the

weather, which sometimes made it impossible to land a sufficient supply of materials on the rock, and at other times made it impossible to use them. At such intervals the architect's anxiety was great for the safety of the stones deposited on the rock, but which they had as yet been unable to move beyond the reach of the surf. The loss or fracture of any one of these would have occasioned much delay. The discomfort of wet clothes, and scanty accommodation for drying them, after exposure to sleet and spray, was severe. And yet the grandeur and variety of the surrounding scene, combined with the deep interest of the work in hand, were sufficient not only to compensate for the tedium of occasional inaction, but, in the words of the narrator, "to reconcile him to, nay, to make him actually enjoy, an uninterrupted residence on one occasion of not less than five weeks on that desert rock."

In addition to the magnificent phenomena of inorganic nature, an object of interest was afforded by the gambols of the seal, which is said by report of the neighboring islanders to attain a remarkable size in the neighborhood of the reef. There is something to our apprehension very human in the seal. The voice, the expression of the eye, its known affection for musical sounds, and its docility, and even attachment to individuals, when caught young, give it claims to better treatment than it usually receives from man. The greatest living authority in matters of zoology has conjectured that the strange animal seen from the Dædalus frigate was a seal of the largest (sea-lion) species; that it had probably been drifted into warm latitudes on an iceberg which had melted away, and swimming, poor brute, for life, had neared the strange object, the ship, with some faint original hope of shelter and rest for the sole of its slipper. If Captain M'Quhae could admit a theory which attributes to him and to his officers so large an amount of ocular deception, we are sure he would share our regret at his inability to accommodate so interesting a stranger. The seals of Skerryvore made no such demand on Mr. Stevenson's hospitality. They enjoyed the surf which menaced him with destruction, and revelled in the luxuries of a capital fishing station

They moved in tracks of shining white;
And when they reared, the elfish light
Fell off in hoary flakes.

Perhaps, like the Ancient Mariner, he "blessed them unaware;" but thus he writes of them :

Among the many wonders of the " great deep" which we witnessed at the Skerryvore, not the least is the agility and power displayed by the unshapely seal. I have often seen half a dozen of these animals around the rock, playing on the surface or riding on the crests of the curling waves, come so close as to permit us to see their eyes and head, and lead us to expect that they would be thrown high and dry at the foot of the tower; when suddenly they performed a somersault within a few feet of the rock, and, diving into the flaky and wreathing foam, disappeared, and as suddenly reappeared a hundred yards off, uttering a strange low

the "

cry, as we supposed of satisfaction at having caught | served. The torch in Hero's tower, and the telea fish. At such times the surf often drove among graphic fire-signals so magnificently described in the crevices of the rock a bleeding cod, from whose Agamemnon" of Eschylus, could hardly back a seal had taken a single moderate bite, leaving the rest to some less fastidious fisher.-P. 157. have failed in times anterior to the Pharos of Ptolemy to have suggested the use of continuous In July, 1841, as the masonry rose to a height lights for the guidance of the mariner. In later which made the stationary crane difficult and even periods, when the coasts of France and Britain unsafe to work, that beautiful machine, invented were more frequented by the predatory northman for the Bell Rock, and which rises with the build- than by the peaceful merchant, and when the haring it helps to raise, the balance crane, was brought vest of shipwreck was considered more profitable into requisition with all the efficiency and success than the gains of commercial intercourse, it probdescribed in the narrative of the elder Stevenson. ably often appeared to the inhabitants of the With such aid the mass of masonry built up dur- seaboard more their interest to increase than to ing this working season amounted to 30,300 cubic diminish its dangers. It is related of one of the feet-more than double that of the Eddystone, and Breton Counts, St. Leon, that, when a jewel was somewhat more than that of the Bell Rock tower. offered to him for purchase, he led the dealer to a Such was the accuracy observed in the previous window of his castle, and, showing him a rock in dressing of the stones in the work-yards on shore and the tideway, assured him that black stone was in their collocation by the builders, that the gauged more valuable than all the jewels in his casket. diameter of each course did not vary from the cal-The only modern work of consequence anterior to culated and intended dimension one sixteenth of an the Eddystone, cited by Mr. Stevenson, is the Tour inch, while the height exceeded that specified by de Cordouan, situated in the mouth of the Gaonly half an inch. Mr. A. Stevenson only does ronne some two leagues from Bordeaux, which in justice to his father in stating that much of the respect of altitude and architectural grandeur and comparative rapidity of his own work was due to embellishment remains, as Mr. Stevenson says, the the steam attendance at his command. No death noblest edifice of the kind in the world. Whether from accident or injury occurred during the entire that embellishment be as well suited to the subprogress of the work-but the loss of Mr. Heddle, ject-matter as the severer grandeur of the curvicommander of the steamer, who died of consump-linear towers of Smeaton and the Stevensons, may tion in the course of the winter, was probably due be questioned. Commenced by Louis de Foix, to exertion and exposure in that service. On A. D. 1584, in the reign of Henry II., and finished the 21st of July the last stones for the tower were landed under a salute from the steamer. On the 10th of August the lantern was landed. It was, however, impossible to do more this season than to raise and fix it, and cover it with a temporary protection from the weather and the dirt of seafowl for the winter.

The summer of 1843 was occupied in repointing the joints of the building—a tedious operation conducted from suspended scaffolds-and in fitting the interior. It was not till the 1st of February, 1844, that the light was first exhibited to mariners. For reasons most ably and minutely detailed in a concluding chapter, the apparatus adopted was identical in its general arrangements with thatin the main dioptric, but combining some of the advantages of the catoptric system of illumination —which had been applied for some years before to the Tour de Cordouan. The light is revolving, appearing in its brightest state once in every minute. Elevated 150 feet above the sea, it is well seen as far as the curvature of the earth permits, and even at more than twice the distance at which the curvature would interfere were the eye of the observer on a level with the sea; for it is seen as a strong light from the high land of the Isle of Barra, thirty-eight miles distant.

in 1610 under Henry IV., it exhibits that national taste for magnificence in construction which attained its meridian under Louis XIV. The tower does not receive the shock of the waves, being protected at the base by a wall of circumvallation, which contains also casemated apartments for the attendants. Hence a construction in successive stages and angular in the interior, consequently less adapted for solidity, but more susceptible of decoration, than the conical, has for two centuries stood uninjured. In this, as in our own lighthouses, the inventions of science have been gradually substituted for the rude original chauffoir, or brazier of coal and wood, such as within memory was in use in the Isle of May. In the latter case it is supposed to have led to the destruction of two frigates, which mistook for it some kilns on the coast, and ran ashore on the same night near Dunbar. The Tour de Cordouan has, in our times, been made illustrious by the first application of the dioptric contrivances of Fresnel, which Alan Stevenson has borrowed, not without ample acknowledgment, nor without some improvements, for the service of his own country.

Mr. Stevenson, while treading in the footsteps of Smeaton and his father as historians of their great works, has largely availed himself of the In a chapter which Mr. Stevenson devotes to progress which has taken place in the art of enthe general history of lighthouses, he has col-graving. It is amusing in Smeaton's folio to oblected the few and meagre notices which remain to us of those constructed by the nations of antiquity. We can hardly doubt that some must have existed of which no record has been pre

serve the costume of days when the rough business of life was transacted under wigs and in shorts and shoebuckles; but the lapse of time is no less apparent in the delicacy and beauty of the

modern illustrations.

On no part of his work has tain number of Argand lamps are disposed on a Mr. Stevenson been more lavish of this useful and frame-work, each in front of a metallic reflector, instructive adjunct to a pregnant text than in the which latter is always moulded to a parabolic treatise which he devotes to the curious subject of curve. Both in this and the dioptric system the the illumination of lighthouses. No such assis- first great division adopted for the important purtance, indeed, can bring a disquisition so pro- pose of distinction and identification is into fixed found and such an array of mathematical science and revolving lights. The catoptric system, by within the grasp of the unlearned. It needs, the aid of various contrivances, has been made however, but an uninstructed glance at these susceptible in practice of nine conspicuous and unpages to show that when the engineer rests from mistakeable varieties; for which differences of his architectural labors he has further difficulties to encounter and problems to solve, which require an extraordinary combination of theoretical science and practical skill. The Promethean task remains to which the construction of the corporeal frame is but subsidiary. It may at first appear a simple matter to accumulate within a limited space instruments and materials of luminous combustion, and to trust to the unassisted laws of radiation for the diffusion of the light produced. The result, however, of this process would be to direct an immense proportion of the rays in sheer waste towards the zenith or the centre of the earth. It becomes the business of the engineer, no longer an architect but an optician, to control the rays and to direct their divergence on the system best suited to the local conditions of the edifice, to adapt the range of visibility to the circumstances of the navigation, and to give a specific character to the flame which shall enable the mariner, without hesitation or mistake, to distinguish it from others. It is laid down by Mr. A. Stevenson that no two lights similar enough to be confounded should be placed on the same line of coast nearer than one hundred miles to each other.

The various inventions which have been, with a view to these various objects, substituted for the candles of Smeaton and the brazier of the Isle of May are of recent date. Many of them were, as is usual, preceded by those vague suggestions which often put in a claim for original invention, but scarcely diminish the honor of successful accomplishment. Among the names of those who have contributed most effectually to the present efficiency of the system of marine illumination, Argand, Borda, and Fresnel are conspicuous. The hollow cylindrical wick of the first was a sudden and immense advance in the art of economical and effective illumination. The second applied the parabolic mirror to the light of Cordouan-an invention which has multiplied the effect of the unassisted flame in the case of a fixed light by 350, in that of a revolving light by 450. For the merits of that great master of the more complicated system of the refracting lens, termed the dioptric, Fresnel, we must refer our readers to Mr. Stevenson's pages and their elaborate engraved illustrations. It may, however, for the benefit of that portion of our readers whose comprehension of optical contrivances cannot be assisted by the use of Greek terminology, be permitted to us to state here in few words some of the leading and distinctive features of these two systems of illumination. In the catoptric, a cer

color, periodical gradations of splendor, and absolute temporary occulation are the means employed. The relative arrangement of the lamps with their reflectors to each other differs according as the light is fixed or revolving. In the fixed light the lamps and reflectors are disposed on a circular frame with the axes of the latter inclined to each other at such an angle as shall enable them to illuminate as completely as possible every quarter of the horizon. The revolving light is produced by the revolution on a central shaft of a frame with three or four sides, on each of which the reflectors are disposed with their axes parallel. One variety, indeed, the flashing light, is produced by a somewhat different arrangement, involving an inclination of the axis of each reflector to the perpendicular. In the dioptric system a powerful burner is placed in the centre of a frame, usually octagonal, fitted with a refracting lens to each of the sides.

Contrivances of great ingenuity and complexity have been superadded by Messrs. Fresnel and Stevenson both for reflection and refraction of much of the light, which, without their aid, would be wasted in an upward or downward direction, entitling the whole apparatus, combining, as it then does, the qualities of the two systems, to the designation of catadioptric. We are sorry to confess that, in spite of the removal of those vexatious excise regulations which so long paralyzed the glass manufacture of England, we are still dependent on France for the glass used in the construction of our dioptric lights. Mr. Stevenson has entered fully into the subject of the comparative merits of the two systems. For lights of the first order in range and importance, specified by him—as those which are first made on oversea voyages-and which embrace within their action a large portion of the horizon-it seems clear that the dioptric system is to be preferred. In respect of intensity, equable diffusion of light in the direction required, and economy of oil, it has decidedly the advantage-in the latter particular in the proportion of three and a half to one. The consequence, however, of extinction from accident is, as Mr. Stevenson terms it, infinitely great in the case of the one central burner of the dioptric system as compared with that of the numerous lamps of the catoptric. There are also cases, such as those of fixed lights in narrow seas, where it is only needful to illuminate a limited segment of the horizon, in which he prefers the reflected light. He condemns the employment of colored media on the score of absorption, and

considers it only admissible in the case of a line and economy may be fairly consulted. Our chilof coast crowded with lighthouses in which the dren, perhaps we ourselves, who remember the other and better processes of revolution and tem-old lamps and older watchmen of London, may porary occulation have been exhausted. In such live to read gas-shares at a discount, and to see the red glass may be used, but blue and green, the nocturnal duty of the policeman simplified by from their greater absorption, are not entitled to the radiance of artificial suns which shall fill whole promotion from the shop of the apothecary. regions of streets and alleys with light from one central source.

The critical position and permanent requirements of the lighthouse make it improbable that Apart from such extended speculations, we conthe oil-lamp will soon be supplanted on the sea-sider it not unlikely that the experiments pursued girt tower either by gas or by any of those still and the processes adopted for marine illumination more recondite devices which are almost daily may suggest minor improvements which, though engendered by the advancing chemical science of of less importance, may conduce to public and the age. Gas, indeed, has sometimes been ap- private convenience. The house of lords, clubplied to marine-lights on the mainland. For the rooms, and other large enclosed spaces, have been dioptric-light, where there is one large central assisted by Mr. Faraday and others by various flame, it possesses, at least, two decided advan-methods to get rid of unhealthy gases and supertages the form of the luminous cone is less fluous caloric. The great saloon of Lansdowne variable, and the inconvenience of mechanism in House has, if we mistake not, long been partially the lamp is avoided. These advantages are, how-lighted on festive occasions from without; and ever, more than compensated in all positions to Lord Brougham, we hear, has lately availed himwhich access is difficult and precarious, by the self of a similar resource in the old hall of his difficulties of the manufacture of the gas and seat in Westmoreland, without at all disturbingtransport and storing of fuel; perhaps in all cases on the contrary, aiding and enhancing-its imby the risk, however reduced by modern inven- pressive character. We are not aware that any tions, of explosion. For the catoptric revolving- attempt has yet been made towards the effective light it is obviously unsuited. illumination of a large room without any interior combustion. We understand, however, that Mr. Barry has such an attempt in contemplation for the picture-gallery at Bridgewater House, and

Cordouan and the Bell Rock. Guttering-candles and broiling-lamps are behind the age we live in, and we have every reason to wish Mr. Barry success.

We cannot attempt the delicate task of a biography of living worthies. The peculiar line in which the two Messrs. Stevenson have attained eminence sufficiently distinguishes them from that family of English engineers who have made illustrious a name so nearly similar, that confusion between them and their respective achievements might otherwise possibly arise. It is a satisfaction to us, however, to

To the Drummond and Voltaic lights there are other objections than those which adhere to any process involving delicacy of adjustment and manipulation. A full exposition of those objections this by the aid of the parabolic reflector of the would require some of that mathematical disquisition and graphic illustration which Mr. Stevenson has lavished in his pages for the use of the learned. It is sufficient here to explain that, to fulfil the purpose of a marine light, whether fixed or revolving, some degrees of divergence are essential -that to produce this divergence, and to control and direct it either by the mirror or the lens, a body of flame, as distinguished from a luminous point, is equally necessary. Such operators as the Fresnels and Stevensons leave nothing to chance to any chance, at least, but that of fog or violent accident. That effect, whether of slow-relate, that the architect of the Bell Rock, having ly-increasing and waning splendor, or of fixed radiance, which at the distance of twenty miles cheers the spirit and directs the judgment of the mariner, is previously calculated and rigorously governed by so small a quantity as the measured diameter of the cylindrical wick placed in front For the last century England has been a great of the mirror or behind the lens. If this diame- school for the practical application of mechanical ter, as in the case of the Drummond and Voltaic science. It is somewhat curious to compare the processes, be reduced to a luminous point, of how-present condition of her intellectual resources in this ever concentrated and increased intensity, practical department with those of the earlier attempts to utility is annihilated. An experiment was made by Mr. Gurney in 1835 for adding power to the flame of oil without reducing its dimensions by a combination with oxygen, but the plan was rejected by the Trinity House.

Such, however, is the intensity of the light produced by some of these processes, that we cannot despair of their ultimate application to purposes and situations which afford a safer field for ingenuity, where accident is of less consequence

retired from the office of engineer to the Northern Lights, is still enjoying an honorable repose in Edinburgh, and that his son and successor in office is at present superintending the building of five lighthouses in Scotland.

light the Eddystone-the proceedings and results of solid instruction with the desultory efforts of amateur ingenuity. A country gentleman and a silkmercer were the predecessors of Smeaton at the Eddystone. The first, Mr. Winstanley, had distinguished himself by a talent for practical mechanical jokes, which must have made his country house in Essex an agreeable and exciting residence for an uninitiated guest. You placed your foot in a slipper in your bed-room, and a ghost started up

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