« 이전계속 »
centre pillar, by the aid of which the whole are firmly tied and braced together —the top of the pillars stand about four feet above high water mark of a spring tide. The timber framing was commenced by first fixing the centre post twentyone feet long and fourteen inches square, and subsequently those of the angles, thirty feet long, twelve inches square at the base, and ten inches square at the top; they are tied together at the bottom by double horizontal tie beams, twelve by five, and twenty-seven feet long, and at the top ten by four, and twenty-one feet long; the ends are secured to the angle posts by wrought iron nuts and screw bolts and iron knees. There are also raking braces from the angle posts to the centre ten and a half by nine, and fifteen feet long; upon the tie beam* are laid the flooring joists nine by three, the principal posts of the carcase framing are six by four.
The interior accommodation consists of a living room twenty-two feet long, and a store-room in the upper part, and store-rooms for coals and water in the lower part Thus far the erection was completed in October 1840, within a period of three months.
Above the living room is fixed the lantern with a gallery all round—it is a polygon of sixteen sides, twelve feet diameter internally, and sixteen feet high from the floor to the roof; the principal part of the framing is of cast iron—the roof, the interior lining and floor are covered with copper. In the centre, upon a pedestal, is the beautiful apparatus of a second order of Dioptric light, made and fitted up, together with the iron work of the lantern, by Messrs. Wilkins and Son, of Long Acre. The height of the light above the mean level of the sea is forty-five feet, and may be clearly seen from the deck of a vessel, in fine weather, upwards of ten miles off in all directions. The light was first exhibited on the evening of the 10th of February last.
[As the utility and security of this description of light-house has now been tolerably proved, not only in thiB, but in another instance on a sandbank, in a still more exposed situation off the coast of Lancashire, (we allude to the Wyre,) the piles being covered during spring tides to a depth of thirty feet and upwards, we hopo soon to see such structures take the place of those uncertain aids to navigation lightvessels on such sandbanks, as the Goodwin, Hasborough, and many others that surround our coasts, on which there is such an annual sacrifice of life and property. Ed.]
Plymouth Breakwater Light-house.
A light-house is in course of erection upon the western extremity of the Breakwater, the first stone of which was laid by Admiral Warren, on the 22nd of February last, it was designed by Messrs. Walker and Burges, the engineers of the Trinity Board, in July last, and suhmitted to the Admiralty. Shortly after, their lordships gave directions for its immediate construction. It is to be erected upon an inverted arch, the foundation of which is laid about one foot six inches below the level of low water spring tides; its centre at top is at the distance of thirty-seven feet six inches from the western end or head of the Breakwater, and at the level of low water 195 feet. The diameter of the head of the Breakwater at the level of low water is 390 feet, and at the level of the top of the Breakwater seventy-five feet. The light-house is to be of granite fourteen feet clear diameter, the centre of the light will be fifty-five feet from the top of the Breakwater. The interior will be divided into floors, forming a •tore-room, a dwelling-room, a bed-room, and a watch-room. The lantern twelve feet wide and seven feet six inches high, is to show a Dioptric fixed light of the second order, with mirrors; the south half to show a red light, to distinguish it from the coast lights, and the north side towards the Sound, is to be white. The stones of the lower courses are to be secured with dowels of slate, independent of a vertical and horizontal dovetail; the dowels are eighteen iuches long and six inches square at the centre, and sunk eight inches into the lower course of stone; both ends are dovetailed and secured in their places by plugs in the upper, and by wedges in the lower stone. It is expected that the light-house will be completed by the end of 1842.
ENLARGED SERIES NO. 5.—VOL. FOR 1841. 2 X
Plymouth, March 4 th, 184!. Sir.—The manner whereby seamen ascertain the nature of anchoring ground in unfrequented, or imperfectly known roadsteads appears to me to be very unsatisfactory. The usual method is to arm the lead with a little tallow, which brings up from the bottom a portion of the soil; a conclusion is then drawn of the quality of the bottom forming the anchorage. It must, however, be apparent that this method only shews the nature of the soil forming the superstructure at the bottom, and therefore, a single inch in depth of fine sand may cover hard rock, and thereby indicate anchoring ground where none really exists! The excellence, or otherwise, of holding ground must obviously depend on the quality as well as quantity of the soil forming the bottom of the sea.
A very simple and cheap machine was used by me for testing the anchorage in Plymouth Sound, and as every ship might get one made for a few shillings, it is surely desirable one should be onboard to try the nature of any bottom wherein it may be expedient to anchor.
A B is a bar of iron about one inch and a half square, j^g Eye for line. and three or four feet long, with an eye at A, and pointed with steel at B. C is aknobof iron to increase its weight, and from C to B the graduated scale will shew the depth to which it enters the soil, and when greased the quality will be ascertained.
This machine should be as heavy as a deep-sea lead, and when thrown overboard will descend point downwards, being guided by the line: on entering the soil, the graduated scale will shew the depth to which it has descended: the barbed notches on the side, or its greased surface, will indicate the quality of the bottom.
I take this opportunity of giving a very useful bint relative to anchoring on rocky ground, which is now often done with chain cables. Seamen are seldom geologists, and their attention may probably be drawn to the subject. The rocks forming the cliffs on a coast are generally of the same kind as those forming the bottom of the adjacent sea. Now the dip of the stratified rocks may be seen above water, and hence the dip of the rocks lying under water may be inferred.
The dip of all the rocks near Plymouth is toward the south, and the rugged top towards the north (the Mewstone is an example.)
Let S. N. be a section of the stratification near Plymouth, dipping from north to south; it is evident an anchor might be dragged from south to north, with little chance of hooking the rocks; but if dragged from N. towards S. against the grain, it would soon meet with resist
^h6' £nd W°uld either hold on' or be hroken- Now this is precisely wnat happens at Plymouth, whenever ships anchor over parts of the bottom that has been scoured by the tide, they drive northward ; but in driving the other way the anchors or cables soon get fast among the rocks.
Those, therefore, who are compelled to anchor on a hard or rocky bottom should have an eye to the dip and stratification of the rocks on the adjacent shore, and calculate accordingly. It would be an improvement in chart making to insert the dip of rocks upon the coast, and also their geological character.
I am, &c.
To the Editor of the Nautical Magazine. Queen't Harbour-master.
Collision Of Steamers With Sailing Vessels.
City of Dublin Steam-packet Company's Works, Clarence Dock, Liverpool, 5th April, 1841. Sir.—Having been a subscriber for many years to your valuable periodical of course the numerous contributions of" Mercator" have passed under my notice, and althongh I cannot agree with that writer in a vast number of the opinions which he has advanced from time to lime, I must, in courtesy, acknowledge that he possesses much talent, and an intimacy with many of the scientific subjects he has treated on.
In your number for April "Mercator" again comes before the public as the writer of a letter on "Collisions of Steamers with Sailing Vessels," in which there appears much objectionable matter founded on manifest erroneous data. He says that the crew of the Gil Bias mistook the light of the steamer, with which she came in contact, for the South Sand Head light; if this were true, I think the owners of the steamer had bard justice dealt out to them by the jury before whom the case was tried, for surely they would not have condemned the Royal Adelaide in damages and other heavy costs, if the crew of the Gil Bias mistook one light for another; such a mistake would clearly take the onus off the vessel carrying the light. But the fact is, and it was proved in court, the steamer had her three lights burning, and the collision occurred from the want of a "rule of the road," in passing in the English Channel.
"Mercator " says in his next paragraph that "a light was observed on board the Nottingham, by the crew of the unfortunate Governor Fenner, and inferences are drawn that one light is not sufficient for a steamer. I will ask Mercator from whence he got his information about a light, for the commander and mate of the Governor Fenner, on arrival in Liverpool, deposed to the editors of several journals, that they saw the " lights of the Nottingham, and they knew her to be a steamer."
In the next paragraph Mercator asks a question, and answers it himself, assuming that if the steamer "had been properly lighted, so as to put it beyond question that she was a steamer,'''' the collision would not have occurred. Now as the Nottingham was properly lighted, having those peculiar lights in action which Mercator himself recommends a little further on in his letter, and as the officers of the Governor Fenner kuew she was a steamer, to what will Mercator now attribute the collision I
As regards th* peculiar lights which Mercator at this latt hour recommends, I have only to observe, that they have been in use on board the steamers plying from the port of Liverpool, since the year 1835, and if Mercator has not seen a description of them in the " report of the Commissioners on steam navigation," ordered by the Admiralty, I would recommend him to refer to it now, if it is only to prove that he is not the inventor;—'tis true Mercator advises the red light to be placed on the starboard paddle-box instead of the larboard one, but what extra security that will give I cannot imagine. But I can imagine that such a change, if made imperative, would cause serious mistakes on this coast, in the same way as putting the helm a port, and thus superseding the rule of starboarding it, as adopted in the Irish Channel for years, has caused many collisions. It has always appeared to me as something very strange, that the East Coast folks are apparently quite ignorant of what is doing on the West Coast.—Is it ignorance? Is it jealousy of the application of inventions ?—the steamers trading to and from Liverpool, have for years been in the habit of starboarding their helms when meeting each other. No rule of any kind has existed on the East Coast. All at once the " body of gentlemen on Tower-Hill," as the Elder Brethren of the Trinity House, are described by Mercator, drew up a series of nautical arrangements, and recommended that steamers should port their helms. To prevent actions for damage in the event of these recommendations not being followed, the rule has been changed here, and collisions have been the consequence. The reason why the plan was adopted of starboarding the helm, was to cause vessels to pass each other as vehicles pass on the high roads and in our street, —the order to port must be bad, because no good reason can be assigned for a deviation from common practice, whether at sea or on land. Again, the steamers trading to this port have for years carried a bright white light under the cross-trees of the foremast,—a bright white light on the starboard paddle-box, and a red light on the larboard paddlebox. Those on the East Coast have never had any denned system of lights, and now a recommendation comes from the "east," to place the red light on the starboard paddle-pox! why, I cannot conceive, but such a change would cause great confusion in the minds of nautical men here, and must lead to accidents of a frightful nature.
Mercator says, the three lights placed as he describes, would form an "equilateral triangle,"—they would do no such thing, they would make an isosceles triangle.
As for Mercator's remarks about steamers not being justified in carrying sails, in the channels of England or on the coast, as an old seaman, and having been seventeen years connected with this Company, I cannot agree in those remarks. Mercator says, "it is pretty clear" that had it not been for the Nottingham's sails, her crew would have seen the Governor Fenner. Again, I am at issue with your correspondent, for how the fore and aft sails of a steamer can prevent men seeing to windward, or over the bows, I am at a loss to understand, for Mercator must be told that the Nottingham was never to windward of the Governor Fenner, on the contrary, she was to leeward of the ship from the moment she was seen to that of the collision. Again, the world is told that steamers are not under command when their sails are set,—indeed! /alwap thought they were less liable to be controlled by their sails than any other craft, but perhaps it is not so.
With respect to the collision between the Nottingham and the Governor Fenner, the facts were, that the three brilliant lights of the former were visible at a considerable distance, whereas, the night being hazy, with rain, it was impossible to see the Governor Fenner, she being without any light, until so close, that the only chance of escape was the starboarding the helm, since to have then ported it would have run both vessels into inevitable destruction. Had the Governor Fenner been a seaworthy vessel she would have received but little comparative damage, but being old and crazy, and unsound, as now appears to demonstration from duly authenticated reports, on the state of the wreck washed on shore and identified,—she was so damaged by the collision that her bottom and stern gave way, and her two sides floated up, gunwale to gunwale, and kept together by the rigging.
I am, &c.
J. C. Shaw, To Vie Editor of the Nautical Magazine. Marine-Manager.
Icebergs Off The Cape.
Ship Seringapatam, Madras Roads, September 20th, 18-10. Sia.—On the outward voyage of the Seringapatam, nearly on the meridian of Greenwich, and in lat. 39° S., we fell in with a great number of icebergs, gome of them very large and dangerous; the ship was at one time completely surrounded by them; if she had struck one during the night nothing could have saved her. The ice was in large solid blocks, and she was going at the time twelve miles an hour with a strong north-west wind. There is every reason to believe what Captain Horsburgh mentions in his East India Directory, " that greater caution is necessary than hitherto supposed, for it seems very probable that some missing ships have been lost by striking against icebergs in the night, during tempestuous weather." August 7lh, 1840, at daylight saw a large iceberg, and at 11 A.m. another larger one; when passing it the ship was going twelve miles an hour.
August 8th; at lh. 30m. P.m. saw a great many icebergs, some of them very large, and all of them evidently breaking up, with a great many loose pieces of ice; steered accordingly to keep clear of them: at 2 r.M. passed close to a very large iceberg, about one hundred feet high, bearing north: at 2h. 30m. P.m. passed another which upset and turned completely over when nearly abreast of it, at the same ttme one in sight to the southward, the largest of any seen, with a number of smaller ones; the ship completely surrounded by icebergs and pieces of ice : at 3h. 30m. P.m. no more ice in sight to the eastward from the masthead; kept a good look-out but no ice seen: at 7h. P.m. hauled the courses up and double-reefed the topsails, reefed the mainsail, and kept the ship's head to the northward under topsails during the night, and a good look out: wind north-west to W.S.W., blowing hard and squally; at daylight no ice in sight, "teered E.S.E. by compass, and made all sail. At noon, lat. 38" 17' S., long. 59' E—When the ice was first seen the ship was going twelve miles an hour, and if she had struck one of the icebergs she must nave been knocked to pieces.
1 shall feel obliged by your giving this publicity, as it will caution all commanders of vessels running iu those latitudes to keep a good look out; as I am