“SWINGING THE SHIP.” A VISIT TO THE COMPASS OBSERVATORY.

The noble ship with her floating battery of heavy guns, her hundreds of seamen, smart and brave, her powder, shot, and shell for destroying an enemy, and her tons of provender to supply her crew; with her anxious captain and aspiring lieutenants, mates, middys, warrant officers, and her pipeclayed marines are on board. The long pennon whips the winds; the hurry, bustle, and noise of preparation has subsided into the quietude of everything in its place; when the word passes that she is “Ready for Sea.”

Next morning the newspapers find just a line and a half in their naval corner for the announcement,—“Her Majesty’s ship Unutterable, 120 guns, went out of harbour yesterday. After she has been swung, and had her compasses adjusted, she will sail for the Pacific.”

“Swing a hundred and twenty gun ship?” says the good citizen interrogatively to himself, as he devours his coffee and his newspaper at breakfast. He pays his taxes and is proud of Britannia and the British navy, but his admiration of the nautical does not help him to a solution. “After she has been swung!” he repeats, and then more immediate affairs draw off his attention, and he leaves the Unutterable to undergo the mysterious. He turns to the debates.

Naval officers are of course more wise on the point, and some of them have more knowledge of the operation than liking for it. It’s apt to spoil the paint now and then, and gives trouble, and upsets some of their arrangements. Many, it must be confessed, have more experience than science in their composition, and when they let out their true feeling, indulge, perhaps, in a half growl, in which the words “new-fangled” and “deal of trouble” might be heard. But the operation goes on nevertheless, and little doubt but the toil is forgotten and the growl repented when—far, far at sea, a murky sky shuts out the sun and the stars, and forbids heaven to tell the navigator where he is—with a waste of waters, hundreds, perhaps thousands of miles around him, he has nought but his figures and his little trembling needles of magnetised iron to guide him on his way; to direct him wide of the sunken rock and the sandy shoal as he nears the wished-for coast.

The loss of British ships by wreck has been stated at between five and six hundred in a year—or about “a ship and a half-a-day.” This terrible loss has been ascribed to many causes—to the tides and currents of the ocean; to imperfect logs; inaccurate charts; unsteady steerage; inattention to the lead; stress of weather; defective ships, and defective management; but last, if not greatest, says Captain Johnson, who gives this catalogue of sources of disaster, we have the errors of the compass. These errors were noticed—now nearly a couple of centuries ago, and from those days to the present time careful mariners have often called attention to the subject. “Officers in charge of convoys during the war,” continues Captain Johnson, “will probably remember the care with which the general signal was displayed at sunset, to steer a given course during the night,” with what alacrity that signal was repeated by the ships of war in their stations, and answered by every merchant-vessel in the fleet; and they will also possibly remember with what surprise,—nay, indignation,—they observed when daylight came, almost the entire convoy dispersed over the ocean as far as the eye could reach, and mayhap a suspicious looking stranger or two escorting those farthest away, further astray, in despite of all the shots fired during a morning watch to recall them. That such dispersements were in part attributable to the differences of the compasses in each ship, there can be no doubt; but the greatest delinquents in this particular, in all probability, were not the merchant vessels, but rather the ships of war; the attractive power of their guns upon the compasses being now a well-known and constantly proved fact.

The Apollo frigate, and forty merchantmen of her convoy, in 1803 were wrecked together on the coast of Portugal, when they believed themselves to be two hundred miles to the westward. The error of the frigate’s compasses is believed to have been the cause of the disaster; and a similar belief exists with respect to the dreadful wrecks of our line of battle ships on the coasts of Jutland and Holland in 1811. The wreck of the Reliance, Indiaman, on the coast of France, when one hundred and nine lives were lost, in 1842, is another painful accident ascribed to errors of the compasses induced by the presence on board of a large iron tank forty-six feet long, the attraction of which had been overlooked—for a hollow tank has a magnetic influence as great as a solid mass of the same external dimensions—and such a mass would weigh four hundred and sixty-eight tons.

These errors in the needle that guides the ship, so dangerous in their results, at last attracted official attention in England. Inquiries were extended in various directions, and it was found that “in some ships the deviation was small; in others it was large enough to cause the loss of a ship, even during a short run; whilst in others, again, from the position of some iron stancheon, bolt or bar, or stand 415of arms, the error might be changed in the opposite direction; so that the deviation in one vessel was not a guide to its amount or direction in another; and that there was no other remedy but ascertaining the fact by direct experiment in each ship.” These facts were recognised by a committee of English officers, appointed to investigate the matter, one of whom was the Captain Johnson whom we have already quoted, and of whose subsequent labours we shall have further presently to speak.

With these words of explanatory preface, let us set out on a visit to the establishment where the dangers of those afloat are sought to be lessened by scientific investigations on shore.

About two miles and a half eastwards from the Greenwich Observatory, in the picturesque parish of Charlton, and on the extreme corner of the high land that runs from Blackheath, till it juts out close upon the banks of the Thames—stands the building we are in search of. Those who may try to discover it will probably find some little difficulty in the task, for the place is unpretending in outward aspect, and is little known in the neighbourhood; has never before been publicly described—except, perhaps, in those unread publications called Blue Books, and in the technical volume of the naval officer who has charge of this sanctum of science.

It is called the Compass Observatory; and its locality may probably be more completely indicated by saying that it is not very distant from, though on a far higher level than that corner of the Woolwich Dockyard whence the great chimney soars up like a rival monument to that on Fish Street Hill, and where the engine that sets the Dockyard Machines in motion hums like a bee of forty-horse power. When the place is reached, those who expect to see “a public building,” will be disappointed; those who like to find that Science may abide in small and humble places, will be pleased. A long strip of newly-reclaimed land, a detached brick house, and in its rear, an octagonal wooden structure of little greater outward pretensions than a citizen’s “summer house,” make up the whole establishment.

Passing under the pleasant shade of two fine oak trees, and then between a collection of very promising roses, we enter the house. Once inside, we see that the spirit of order, regularity, and neatness, is there paramount. The exactitude requisite for scientific observation, gives a habit of exactness in other things. In one room we perceive a galvanic battery ready for experiments; a disc of iron for showing a now defunct mode of steadying the vibrations of the compass; a specimen of the mixed iron and wood braced together as they are now employed in the construction of first-class ships of the Royal Navy, like the Queen’s Yacht; and more, interesting than all the rest, a copper bowl, contrived by Arago, for stilling the irritability (so to speak) of the magnetic needle.

The French astronomer and ex-minister of the Provisional Government here claims our admiration of his scientific skill, and his work suggests the reflexion how much more pleasant the calm pursuit of nature’s laws must be to such a man, than the turbulent effort to enact rules and constitutions for an impetuous and changeable people. Passing from this room to another, we find books, and charts, and maps, on which are laid down the magnetic currents over the great oceans, and amongst its instrumental relics, a magnetic needle that belonged to poor Captain Cook. It is a plain small bar of steel in a rough wooden case, but to the mariner who loves his craft and its heroes, this morsel of iron has an interest greater than the most perfect of nautical inventions—for Cook was a seaman who achieved great ends with humble means and from humble beginnings. A third room is full of compasses of all sorts, sizes, and kinds, from China, from Denmark, from France; from the most rude and simple, to the most complex and finished. All the schemes and plans ever proposed for improving this useful invention are here preserved. Many of the contrivances have been discovered more than once. A sanguine theorist completes what to him is perfectly new. Certain that he is to be immortalised and enriched, he sets off to the Observatory with his treasure, to reveal his grand secret, and receive the anticipated reward. He is shown into the compass-room, and there,—horror of horrors,—upon the table, amidst a host of others, there is an old discarded instrument the very counterpart of his own! It was made, and tried, and discarded, years ago.

From the main brick building we pass through another line of roses, and under a bower, boasting some fifty different varieties of that charming flower, to the wooden structure in the rear, which is, in fact, the Observatory.

This building is entirely free from iron. It is approached by stone steps; the door has a pure copper lock, which being opened by a copper key, swings on copper hinges to admit the visitor after he has first cleared the dirt from his shoes upon a copper scraper. Nearly facing the door is a stove to keep up the temperature in cold weather. It looks black enough, and has a black funnel. When the visitor is told that Captain Johnson has his coat-buttons carefully made without any iron shank concealed under their silken cover; and that his assistant, Mr. Brunton, repudiates buttons to his jacket altogether, and has pockets guiltless of a knife; he is apt to turn to the stove, and hint the presence there of the forbidden metal.

“Ah, ah!” is the reply, it looks like iron sure enough; but the fireplace, the chimney, the poker, the shovel, are all alike. Nothing 416but copper, copper, pure copper. This suggests an anecdote. When the operations in this Compass Observatory were first commenced, there was found to be a small variation in the magnet. The instruments were readjusted; their character was investigated, their construction re-examined; other observations were made—but still the variation continued. Pockets were searched for knives; the garden looked over to see that no stray spade or rake had been left outside the building, yet near enough for mischief. Nothing could be discovered. At length the brass bolt on the window was suspected; and though brass had a good character, not being thought capable of coaxing the magnet from its truth, it was, in despair of finding any other delinquent, unscrewed from its position. No sooner was this done, than the wayward needle returned to its true position; the brass bolt was ejected in disgrace, and no morsel of the brazen metal has since been allowed to show itself within the precincts of the building sacred to the mysterious fluid that draws the iron needle to the North.

Once inside the Observatory, the first impression is one of isolation and quietude. Look up to the wooden roof, and you see two shutters, to be opened when an observation is to be made upon a star. Through the floor rise three pedestals of masonry, built solidly from the earth, and isolated from the Observatory floor, so that no vibration may be communicated to them. All three stand in a row, running north and south. The object of two of them is to support with complete steadiness and truth two instruments for determining, at any moment of time, the exact magnetic north, whilst the third pedestal holds one by one the compasses brought there to be tested. The most northern of these three narrow stone tables is, in fact, a bed of trial—a place of ordeal—whilst the other two support the instrumental judges, who are to pass sentence upon the fluttering needles brought under their unyielding gaze. The test is a severe one. It is easy, with proper means, to get the true magnetic north with a fixed instrument on shore, but to make something that shall tell it with equal truth upon the deck of a ship, as it heaves and tosses, and plunges on the sea, is a very different thing. Yet, instruments equal to such triumphs of skill are obtained, and in this place it is that their qualities are first investigated. The south pedestal has upon it a tall tube of glass, within which there hang some long fibres of untwisted silk, supporting a magnetic tube so beautifully poised, that it obeys without let or hindrance its natural tendency towards the magnetic north. This tubular magnet has at one end a glass on which a scale and figures are engraved, but so fine and small as to be with difficulty seen by the naked eye. The second pedestal supports a telescope, with which the observer looks down the tubular throat of the magnet towards this tiny scale on the glass at its extremity. Our friends, the “spiders,” have contributed some lines to the telescope, and the centre one of these crosses the exact figure showing the magnetic position at the moment.

With this figure in his mind, the telescope and the observer’s eye are poised in the opposite direction, through the window of the Observatory, towards a spot some half mile to the north, called Cox’s Mount; an eminence on which a wall has been raised to bear a numbered scale similar to that on the magnet—with this difference—that the one is very minute, and the other very large. To the corresponding figure on the distant wall the instrument is directed, and being thus pointed towards the true magnetic north, it is brought to bear upon the pivot of the compass—which by this time occupies a place on the top of the third pedestal to be tested. Without a complex description, and the free use of scientific terms, it would be perhaps impossible to convey a thoroughly exact conception of the steps of the whole process. Such a detail would be not only too technical, but unnecessary, here. It will be enough in general terms to say, therefore, that the indication obtained from a star, or from the instrument on the south pedestal, called the collimator, is, by means of the instrument in the centre, combined with a mark upon a distant object, and then brought down to prove the true powers of the compass placed on the third pedestal. It is a beautifully exact operation. The silence of isolation, the steadiness of stone tables and practised operators, the most beautifully constructed instruments, are combined to ensure accurate realities as a result. The tests are so varied, and so often repeated, that no error can escape, and the compass, when it leaves the building to begin its adventures afloat, commences its career with an irreproachable character as a Standard Compass of the Royal Navy—to be, on board the ship of war to which it is sent, a kind of master instrument of reference, by which ruder and cheaper compasses may be checked and regulated.

Just as the history of the stars and of the variations of the magnet is registered and posted up at the Greenwich Observatory, so is that of the compasses entered up here. Every compass that passes its examination may be said to receive its commission, and be appointed to a ship. Its number is taken; its vessel and destination are noted, and, subsequently, its length of service. On its return home from successive trips, it comes back to this place, when its character is again investigated and note made of any loss of magnetic power, of any deviations it may have exhibited, how it may have lost and how gained, and of any other circumstances showing either improvement or deterioration. Now and then one is blacklisted, but this seldom happens; the greatest loss yet noted being 30 minutes. The Standard Compasses cost, when made new, 417with tripod and all complete, 25l. each. After they have been some years in service afloat, they are sent into hospital for overhaul and repair. This costs generally 4l. or 5l., and they are then again as good as ever, and ready to guide another ship on her way over the mighty waters. The scientific part of the fittings of a ship of war, though of greatest value, are thus of lowest cost. A Standard Compass is, indeed, a beautiful result of human ingenuity. Generations of seamen and men of science have discussed the best form and materials, and the best mode of suspending the needle, that it may most freely and truly follow its mysterious love for the north. From the days of the old adventurers round the globe, to the date of the last voyages to the Arctic regions, successive sea captains have thought, and watched, and suggested, and the Standard Compass of the English Navy combines, it is believed, all that is best in all their thinking. After the Observatory was established, and one of its duties had been defined to be to pursue investigations on the deviation of the needle, it was thought desirable to have specimens of the instruments used in the war ships of other naval nations. With the open liberality that unites in brotherhood the scientific men of all countries, France and Denmark sent specimens of what their best men had succeeded in perfecting for the use of their navies. These instruments are very good, and attract deserved attention in the observatory-collection of specimens. The Frenchman is scientific, simple, and with an excellent contrivance for a moveable agate plane to avoid friction in the motion of the needle. The Dane is a good substantial instrument, even more excellently finished than the compasses issued to our navy.

The English Compass is, however, believed with good reason to be the best yet contrived. It has grown up to its present excellence by slow degrees. Human ingenuity has been taxed to its utmost, and it has passed to its present perfection through the various trials of needles of all sorts of shapes swung in all sorts of ways, and by springs, and floating cards, modifying the instrument to the varying conditions of a small boat tossing on waves, or a line of battle ship jarring under the recoil of a broadside. And now we find our Compass-needle made of iron that, being got from the Swedish mines, has travelled to Strasbourg to be prepared for clock springs; thence to Paris, to be still more highly wrought by the watchmaker; and then to London, to take its sea-going shape. Four bars of this choice metal, or of shear-steel of equally fine quality, are ranged edgewise under a card, thickened and stiffened yet kept transparent by a sheet of mica, brought from the Russian mines; this card moves upon a point made of a metal harder than steel, and incapable of corrosion; and which sometimes, under the name of Iridium, but more correctly under that of “native alloy,” is found by the refiners as they smelt the platinum and silver gained from the Ural Mountains or the mines of Spain. The Iridium or alloy comes to the workshop in the tiniest of glass bottles—bottles as small round as a goose-quill, and about an inch long—in morsels not much bigger than a pin’s head, and weighing each less than half a grain. Some of these prove too soft, some too spongy, some too brittle, but at last one is found hard and good, and it is soldered upon the pivot, that, when sharpened and polished, is to work upon a cap, formed of a ruby, brought from the East. A bowl of the metal suggested by the French philosopher being prepared, from the produce of the mines of Cornwall; and the science of the English philosopher, and the skill of the English workman, having brought all these things into their proper shape and places; we have, as the result, the Standard Compass, whose fitness to guide her Majesty’s ship the Unutterable, we have just seen tested by Captain Johnson at the Woolwich Compass Observatory.

Our favourite newspaper has just stated that that gallant ship “is now at Greenhithe waiting to have her compasses adjusted.” So, then, the instruments so accurate at the Observatory a few days ago, are all wrong again on shipboard. Just so. The moment they get to their places afloat, their fidelity to the north wavers,—in one ship more, in another less; but in all in a greater or smaller degree in proportion to the quantity of iron used in the construction of the vessel, and the nearness of that metal to the compasses; in proportion to the number of the iron guns and the total weight of metal carried; to the length of the funnel in steamships, and to the condition of that funnel whether upright or hauled down. All this is both new and strange enough. We have learnt already what loss of ships convoyed and ships wrecked has arisen from these deviations: deviations long neglected on board all vessels and to this hour unrecognised or unattended to in our mercantile marine! Since the Royal Navy, however, has a scientific officer, Captain Johnson, especially employed in attending to the important duty of adjusting the compasses: let us go with him and his assistant, Mr. Brunton, from the Compass Observatory to the anchorage at Greenhithe, and see how he will “swing” the gallant line of battle ship, the Unutterable.

The trip occupies a very short time, for we have steam at command. Arrived in the Reach, we find five floating buoys anchored in the stream, one forming a centre, and four being disposed at equal distances about it, just as the five pips are placed upon a card—say the five of spades. The good ship to be operated upon is already fast by the head to the centre buoy, and Captain Johnson having mounted her deck, and his assistant, Mr. 418Brunton, having been rowed ashore, a rope is run out from the ship’s stern and made fast to one of the corner buoys. The Standard Compass being fixed in the proper position which it is to occupy in the ship, neither too high nor too low, and the guns and other iron being round about it, as they are to remain during the voyage, the mooring ropes are adjusted, and the ship’s head is put due north. Meanwhile, Mr. Brunton has set up a compass ashore, and all being ready, Captain Johnson, at a given moment, observes the bearing of a distant object—the Tower at Shooter’s Hill—noting the bearing of the needle on board. At that instant the pennant that floated at the mast-head is hauled down from the truck. This being the concerted signal, at the same second of time the assistant ashore observed the needle of his compass. The two instruments vary, and the deviation of that on board, compared with that ashore, is due to the iron of the ship. The stern ropes are hauled from one buoy to another, and again made fast, the ship’s head now pointing in another direction. The observations and the signals are repeated. Each deviation of the ship’s compass is carefully noted upon a card previously prepared for the purpose. The ship’s stern is then hauled round to the third outside buoy, and the compasses being again examined, she is next hauled round to the fourth buoy. Her head by this time has been north, east, south, west; on each point the deviations of her compasses have been tested, noted, and the card shows their character and proper adjustment. The ship has been swung. Science has done its best for her, and the word is given to heave anchor, for she is now truly “Ready for Sea.”