Years.

Months.

November.... 1845

9942314

79 2

15 48 11

7 11

52

170 28 326 3016 40 780 1913 279 189 686 1910

Unidenti

fied sing. Vessels

sunk.

London, 59, Fenchurch Street,
May 20th, 1850.

SIR. As the wood cut of the 70 foot galley, built for the use of H.M. consul at Fernando Po, was too late for the last number of the Nautical, I shall feel obliged if you will insert it in your next, and permit me at the same time to offer a few remarks upon the construction of vessels of galvanized iron.

Iron shipbuilding is not yet 20 years old, and has to all practical purposes, superseded wood in that most costly specimen of ship-building, the steam boat. It may be assumed that no private person or company exposed to competition, would in these days venture to build a wooden

steamer.

Iron boat building, by which is meant the construction of ships' boats of metal, has on the contrary failed, from two causes, the rapid oxidation of the thin sheet iron of which the boat must of necessity be constructed, and the weight of the ribs or frames required to support the plates.

The use of galvanized tinned iron obviates the first objection and makes the boat incorrodible, and corrugating the metal does away with the necessity of inside ribs or frames, and enables metallic boats to be constructed lighter, stronger, and more durable than those of wood.

The principle on which galvanized iron becomes incorrodible, is from the action of the atmosphere forming a thin film of sub-oxide of zinc on the surface, which does not dissolve in water, and is so hard as to remain sound when subjected to considerable mechanical friction. The coating of zinc prevents any oxidation of the iron below it, while it is itself protected from decay by the sub-oxide thus formed upon its surface. A

NO. 6.-VOL. XIX.

2 x

boat built of this material may therefore be considered indestructible by any atmospheric influence.

The galley described in the wood cut is the first large boat built of galvanized iron in this country, but they have been and are extensively used in the United States; and in Lieut. Lynch's interesting account of the survey of the Dead Sea, your readers will find a description of a galvanized tinned iron boat, which he took with him for that purpose,

A

Cross Section at A.

and which proved what metallic boats will do in ascending rapid streams like the Jordan, where their wooden boat was knocked to pieces after the ascent of one or two rapids,-while after completing their survey, the metallic boats were again carted across the country to the Medi

terranean.

That the use of galvanized tinned iron will rapidly extend in boat building, now that it is introduced, there can be little doubt, particularly for vessels bound to hot climates, where the alterations of the tempera

ture speedily destroy the best constructed and best protected wooden boats; but I look forward to its being used largely in the construction of ships, for though it is not a complete protection against fouling, it is a partial one, and at the same time a perfect preservative of the metal. I remain, &c.,

MACGREGOR LAIRD.

NAUTICAL NOTICES.

Singapore, Jan. 24th, 1850.

DANGERS IN THE STRAIT OF MALACCA-A first class buoy, painted black and white, having been placed on the 21st of January, 1850, on what is usually called the Two and a half fathom bank, at the western entrance to the Straits of Malacca, in two fathoms at low water spring tides, the following bearings were taken by azimuth compass from it:

Parcilar Hill

False Parcilar Hill

East half South

North 50° East

North 85° East

There is a small patch north-east from the buoy, about twenty fathoms distant, with nine feet at low water spring tides.

About a mile to the eastward of the buoy on the tail of the bank, there are overfalls of three and four fathoms, with five, six, and seven fathoms between them.

To the westward of the buoy, nothing under five fathoms within a quarter of a mile.

To the north and southward of the buoy, there are ten and twelve fathoms within a quarter of a mile.

Vessels from the eastward or westward, keeping Parcilar Hill east a quar ter south will just clear to the southward of the bank, and east three quarters south, will lead a vessel clear to the northward.

S. CONGALTON, Com. H. C. S.

NEW SHOAL IN MOZAMBIQUE CHANNEL.-Mr. White, of the barque Pilot, at Salem, furnishes the following extract from his journal:—“Saturday, Jan. 5th, at 7 A.M., passed over the end of a shoal, with not more than 3 fathoms on it, could see the bottom very distinctly, and at the same time saw several patches to windward, which looked much shoaler. Should think the whole extent of the shoal to be 1 to 2 miles. It bears from Bassas de India N.W.b. W. W., by compass, distant 35 miles, lies in lat. 21° 10' S, long. 38° 57' 30" E., and should consider it dangerous.”—Shipping Gazette.

The positions given by Mr. White do not agree, but they will serve as a CAUTION for seamen.

APPRENTICES.

SIR.-When a boy is bound apprentice to a tradesmen on shore, that tradesman is obliged by law, to teach the boy the whole "art and mystery" of his trade. A boy apprenticed to the master of a vessel ought also to be taught