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MAGNETIC EQUATOR.

THE line of the Magnetic Equator has been hitherto ascertained by the Dipping Needle, which being possessed by few ships, renders observations upon the line very limited. Although less accurate, I conceive a tolerably near approximation to its site may be obtained by means of a soft iron bolt placed upright in the ship, which becoming magnetized by the earth's induction, would consequently denote the particular magnetic hemisphere the ship was in, by approximating one of its poles to the ship's compass, which would of course require to be frequently repeated during the day, when the magnetic power of the bolts' poles was found to be nearly extinct, reversing the bolt each time of trial, and assisting the magnetism by smart blows upon it with a hammer, while held in a perpendicular position. The medium point between which the change of poles took place would of course denote the site of the Magnetic Equator.

Any iron belaying pin might, in case of necessity, be used as a test, a speedy change of poles in all the iron of a ship taking place, after passing from one magnetic hemisphere to another, particularly if some of the cannon be fired in the interim.

C.

WEST INDIA LIGHTHOUSES.

DEAR SIR.-I have now time to give you my ideas on the importance of a lighthouse on the east end of Barbados. This necessity was first agitated many years ago, but in 1835, Sir Charles Smith of the Engineers, and Sir George Cockburn, commanding on the West India station, agreed upon the spot on which to erect it.

The situation was well chosen, to embrace all the important objects in view; first as a land fall from Europe to a large portion of the West trade, including Columbia, and Venezuela; secondly for a very considerable trade from our North American possessions, and the United States, all of which call at the weathermost island first, to try the market before running to leeward, or call "to the order" of their consignee; and thirdly, for the benefit of the trade from British Guiana, which would probably all pass to windward of Barbados, if they could boldly run for a light to enable them to pass in the night time; for want of this they keep away, and at once run to leeward past St. Thomas, which bringing them so far to the westward obliges them also to pass to the westward of Bermuda, where these heavy laden ships are. sure to encounter the worst weather; whereas, if they had passed to windward of Barbados, they could with ease have gone to the eastward of Bermuda; and it is a well known fact the heavy north-west winds from the coast of America, do not extend there in their fullest force, therefore a comparatively fine weather passage is secured. The cur rents too are very unaccountable, though generally setting dead on the Coblers rocks, from the eastward and from the southward; I have been set between forty and fifty to the northward in less than twenty-four hours. This will easily account for the loss since 1835 of sixteen

vessels whose names are known, other numerous pieces of wrecks of vessels names unknown, besides vessels that have grounded, and succeeded in getting off. Why then should Barbados the land-fall of the West Indies be left without that safeguard to navigation a good lighthouse? What is the expense? a mere nothing in comparison to its importance; the estimate given in by Sir Charles Smith for a good solid lighthouse on the plan of the Eddystone, to withstand hurricanes, is 50921. 2s. 6d., on a spot 117 feet above the level of the sea, and being 83 feet more in height. The annual expense of maintaining it is 2317. a trifling duty on shipping passing by, and on vessels coming into the bay (Carlisle) would be willingly submitted to by the shipowners. At Bermuda the preparations for a lighthouse on Gibbs Hill, are in a state of forwardness, and it probably will be completed before the expiration of 1841, by that talented expounder of hurricanes, Col. Reid, the governor.

At Jamaica also a sum of money has been voted, to place a light on Morant Point, which is also in rapid progress in England. Now, I conceive neither of these places require it half so much as Barbados.

I have said the "unaccountable currents," however I do account for them satisfactorily to my own mind. The amazing quantity of water discharged from those great rivers on the coast of Guiana finding its way into the ocean, meets an obstruction to its natural course on the surface by the trade winds, which constantly throwing fresh supplies of ocean water, succeed in forcing the river discharges under, to such a depth, as being no longer acted upon by the face of the winds, this water re-asserts its right of course, and continues on till obstructed again by the island of Barbados; then, it again rises to the surface, and separating into two bodies, occasions that northerly current setting round both the east and west ends, though by far the strongest round the east end and over the Cobler Rocks. The same effect is likewise produced at Tobago, during the heavy rains. I have been set nearly due north seventy miles in the twenty-four hours, being once in the run of it, for probably four or five miles further to the westward, the set of the rivers Orinoco, being rebutted by the island would go off at a rapid rate to the westward, and this I have actually witnessed in a calm with two vessels. In every thing regarding currents in the West Indies, I am quite convinced that the strength of the trade winds would afford a close approximation to the truth; also the dry and wet season to be considered, as well as the direction of the land that may form the opposing power to the course of river discharges.

I have wandered from the lights, and now will resume with my own plan of lighting all the islands in the West Indies. The great object to be obtained by this, is to facilitate steam navigation, now about to be carried into effect on a large scale, and this will be easily shown by explaining that the steam vessels touch at the different islands, at all hours of the night; when, whatever may be the weather, the vessels are obliged to come in close to the shore to receive their passengers, and much valuable property, having from two to three hours only to perform this service, as also to land and take in the mails. In dark nights it is frequently with the utmost difficulty that they can find the land

ing places, therefore, I propose, that a triangular form of light be placed on a post, in the best situation to shew the anchorage, and act as a guide to the landing places. This form will be least likely to be mistaken for accidental lights. It must be remembered, the purpose for which these lights are proposed is not to make land-falls, or warn from distant dangers, but simply as above, to point out the harbours and landing places. The post may vary in height according to the situation in which it is erected, and the lights may be placed so as to serve as leading marks to approach by; that is, on certain bearings a wrong direction may be indicated, by darkening one light or opening out another. With Barbados, a light placed in Carlisle Bay is more particularly required, to enable vessels to anchor at night. It frequently happens in the strong trade winds, that vessels waiting for daylight, are drifted by the current to leeward, and are unable to work up again without standing to the northward, thereby losing two or three weeks. I enclose a rough sketch of the proposed plan, and the estimate on the other side.

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Add to the above expense a shed, for trimming lamps and for the man attending to sleep in, because in the day time he may have other occupations which will reduce his wages.

I omitted to say in some of the islands, I would have the lights coloured, as frequently vessels mistake one island for another, making them at night, carelessly enough, but it does happen.

I shall shortly see the agent for Jamaica, and will then say exactly the sum they have voted, and what the progress they are making with their lighthouse. I remain, &c.,

23, Welbeck Street, 15th Nov. 1840.

W. J. WHISH, Commander, RN.

LIGHTHOUSE FOR MORANT POINT, JAMAICA.

A Meeting of the Commissioners of this Lighthouse took place in Spanish Town, Oct. 28th, 1840.

The clerk of the Commissioners read an extract from the Report of Mr. Alexander Gordon, the civil engineer in London, whereby it appeared that an Iron Tower would be the cheapest that could be chosen, and would cost 8201. sterling. The cost of lantern, lamps, reflectors, and apparatus will be about 1,4507., and fixing the same in lighthouse 150/., making in all 2,4207. sterling. The Commissioners agreed to report to the House; and to request that the Commissioners of Correspondence do communicate with the Island Agent, and request his assistance in carrying the intentions of the Legislature into effect.

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