As iron ship-building has been most suc- cessfully practised in this country for several years past, and as we possess superior ad- vantages over all other countries for the manufacture of that metal, it is surely matter for surprise that we should have made no attempts to use it also in the construction of boats, but have left it to our transatlantic cousins to show us the way. Such, how- ever, is the case; and an American gentle- man of New York, Mr. JOSEPH FRANCIS, has recently patented in this and other European countries, a process for manufacturing boats of corrugated galvanized iron, which, judging from the reports by various authorities, and individuals in the United States, and else- where, appears likely to supersede, to a great extent, the use of wood in the construction of boats. It has, no doubt, been hitherto considered that there were difficulties in the way of the adoption of metal boats, or their construction would long since have been effected by some of our enterprising workers in iron.

The chief requirements of ordinary boats for ships are lightness, tightness, cheapness, durability, and strength; unless, therefore, it could be shown that iron boats would possess these attributes in a greater degree than wooden ones, and especially as regards cheapness, it could perhaps hardly be ex- pected that the old material, with the " prestige " of ages in its favour, should be made to give way to a new and hitherto un- tried one. And, indeed, we incline to the opinion, that without an improvement on the ordinary mode of manufacturing iron vessels by hand, the question would not now arise as to the comparative merits of the two materials, but that wood would still reign supreme in the hands of the boat- builder ; for although, undoubtedly, boats of iron could, by the ordinary mode, be made both tight and strong, yet they would be more costly, and probably heavier, than boats of wood; and misgivings might well be entertained as to the capability of such thin sheets of iron to resist the effects of oxidation from constant exposure to moisture.

Mr. Francis has, however, invented a new principle and method of construction, by which he considers that he has not only overcome the above and all other objections to iron as a material for boat-building, but that boats built by his process possess [all requisite qualities in a greater degree of per- fection than do wooden boats, and have, in addition, the important advantages of being fire-proof, of being unliable to injury from atmospheric changes or exposure to the sun, and of needing no repairs for many years together.

Mr. FRANCIS is not a novice in the art of boat-building, having been engaged in that occupation for 35 years, during which time he is stated to have devoted much earnest and intelligent consideration to improving and perfecting that art, during the first 25 years of which period his labours were con- fined to boats of wood. His invention would, from this circumstance alone, be entitled to serious attention, if it was as yet unproved.

It is not, however, a mere theory, his metallic boats having been in use in the United States' Navy, in their merchant steamers, and as life-boats on their coasts, for several years, during which time they have been put to severe tests, and have gradually increased in favour as their advantageous properties have developed themselves.

The material of which these boats have chiefly been constructed is galvanized iron, although some have been made of copper.

Of the latter description were the boats used by Lieutenant LYNCH, of the United States' Navy, in the exploration of the Dead Sea in 1848, when they were re- ported on by that officer in the highest terms, as having repeatedly descended rapids and cataracts amidst rocks and other impedi- ments without injury, whilst the only wooden boat that accompanied him was almost at the outstart knocked to pieces and sunk. In a letter to Mr. FRANCIS, in March, 1849, Lieutenant LYNCH says:—" With no other kind of boat, however strongly con- structed, could the descent of the Jordan have been accomplished, and the expedition must have been unsuccessful without them." Galvanized iron has, however, been se- lected as the material for ordinary ships' boats, it being much cheaper than copper, and the experience of several years having shown that the galvanizing process, when properly performed, will effectually protect the iron from destruction by oxidation.

The chief feature of Mr. FRANCIS'S in- vention is the adoption of huge cast-iron dies, corresponding in form to that of the boats to be constructed, as shown in the ac- companying illustration. The lower and concave die, forming the matrix, has its surface grooved in longitudinal channels, corresponding in depth and form with the intended corrugations of the metal, whilst the surface of the upper and convex die corresponds with it inversely. The two dies are fixed and nicely adjusted in a power- ful hydraulic press, as shown in the illustra- tion before referred to.

The galvanized-iron plates, of which the boats' sides are to be formed (weighing from 1£ to 2i Ibs. per superficial foot, according to the character of the boat), are placed be- tween the dies, which are then slowly brought together, and submitted by the hydraulic power to an enormous pressure, equal, it is said, to 800 tons. The whole side of the boat, or as large a portion of it as the largest-sized sheet of iron will allow of, is thus stamped into its proper form and corrugated by one simple operation. The permanency of this form and also great strength are secured by the corrugations in the iron, which are likewise so skilfully varied in depth and form as to secure the greatest strength where most required, and to prevent the wrinkling or puckering of the metal in the operation of changing the plane surface of the original sheet to the varying curves of the different parts of a boat.

The two sides of a boat being thus quickly formed, each in one or more parts, according to the size of the boat, they have only to be riveted together, and to the keel, stem, and stern posts, when the boat is formed com- plete, with the exception of the thwarts and other interior fittings which are subsequently added. A vast amount of labour and of consequent expense is thus economized, whilst the corrugation of the iron imparts so great a degree of strength and rigidity to the whole structure, that, except for the conve- nience of rowing, the thwarts might be altogether dispensed with.

As a metallic boat, if swamped, would of course immediately sink, air-chambers are placed within the boat of sufficient size to make her insubmergible in the event of being upset. To that extent, therefore, all these metallic boats are life-boats.

The presumed advantages of FRANCIS'S metallic boats may be thus summed up.

1. That they can be made cheaper than boats of wood.

2. That they are not only perfectly water- tight when built, but that they will remain so under all changes of temperature and climate, or exposure to the heat of the sun.

3. That they are much stronger than wooden boats, and not liable to be stove in, or fractured, by striking on rocks or other hard substances.

4. That they are more durable than boats of wood, and under ordinary circumstances never need repair.

5. That they are fire-proof.

These alleged advantages are so important, that if they should be confirmed by experi- ence hi this country, the metallic boats can- not but, to a great extent, supersede the use of boats of wood; whilst their inventor must be looked on as one of the benefactors of mankind. For how many lives have been lost, from time to time, in boats, from the want of such qualities as those in question are said to possess! We shall await, with much interest, the result of further trials of these boats in this country; not but that those which have already taken place are of the most sufficient and reliable character. The Reports pos- sessed by Mr. FRANCIS in their favour, from various sources, are too numerous for us even to name in detail; they are from the chief proprietor of the COLLINS' line of steam- packets, the commanders of various American steam-ships, and from officers of the navy and public authorities in the United States, who testify to their " economy, durability, and safety"—to their "extreme tightness andyreat strength'—to their " unliability to become nail-sick, worm-eaten, or leaky from exposure to the sun"-—to their being 'fire-proof as well as water-proof" &c. &c.

These reports extend over eight years—a period quite sufficient to ascertain the per- manent qualities of the boats. They have, during the present year, been twice subjected to severe tests in this country by direct/on of the Lords of the Admiralty, to which we shall presently refer. In the first place, however, it may be interesting to our readers to learn the occasion and manner of their introduction to us at the present time; for it appears that but a few months since Mr.

FRANCIS had no intention of visiting this country, being under the impression that distinguished patronage and introductions would be indispensable to foster any such undertaking at its commencement, in order to give it a chance of success.

Mr. FRANCIS had, however, proceeded to Paris, where he has had the honour to intro- duce his plans for building boats, and for the construction of metallic floating military waggons, to the notice of the Emperor of the French, who so highly approved of them, that the following letter, accompanied by a gold box set with diamonds, was, by his Majesty's direction, on the following day, transmitted to Mr. FRANCIS :— " Palais du Tuileries, 4th Feb., 1856.

" Cabinet de 1'Empereur.

" SIR,—The Emperor has witnessed, with great interest, the experiments which have been made in the river Seine with the pon- toon carriage of your invention. His Ma- jesty has also taken pleasure in obtaining in- formation in detail respecting the boat of corrugated metal which you have invented and constructed. The Emperor hopes that your invention may establish in France the foundation of a new branch of industry ap- plicable to the public services for war and for the navy, as well as for the mercantile marine; and his Majesty has advised me to inform you that he will learn with pleasure your determination on this subject.

" I am happy in having to transmit to you the accompanying box, which the Em- peror sends as a testimonial of his satisfac- tion.

" Accept the assurance of my distin- guished sentiments.

" FAVE." We are further informed, that arrange- ments are now in progress in Paris for the establishment of a manufactory of Mr. FRANCIS'S boats and waggons; and that the French, Russian, and Belgian governments have seriously directed their attention to the subject, and will probably, at no distant period, adopt those inventions in their naval and military services.

Whilst at Paris, in July, 1855, Mr. FRANCIS was most fortunately met by a British officer, Major "V INCEST EYRE, of the Bengal Artillery, then on furlough from his regiment in India. Major EYRE was at once struck with the apparent advantages and practicability of Mr. FRANCIS'S inven- tion; apd feeling desirous that his own country should not be backward in possess- ing itself of the advantages, both of the boats and the military waggons, he suc- ceeded in persuading Mr. FRANCIS to visit London, he himself volunteering to publicly lecture on the subject, and otherwise to assist in bringipg the invention to public notice.

Accordingly Major EYRE, in the early part of the present year, delivered, on two occasions, at the United Service Institution in London, an interesting lecture on " Me- tallic boats and army floating waggons," which lecture has been since published by him under the above title, through SMITH, ELDER, and Co., Comhill, London.

Our information respecting the invention has been chiefly obtained from this pamphlet, and Major EYRE has also kindly lent us the zinc plates from which the illustrations of his lecture were taken, which we are thus also enabled to place before our readers.

We would, however, strongly recommend them to procure Major EYRE'S le'cture, which is alike interesting, both as regards the me- tallic boats and the floating waggons, which latter, in a military point of view, are, per- haps, as important an invention as are Mr.

FRANCIS'S boats. Since, however, they are exclusively of a military character, and not connected with the subject of saving life at sea, we shall confine our present remarks to the metallic boats.* Aided by Major EYRE, Mr. FRANCIS likewise brought his invention to the notice of the Lords of the Admiralty, in January of the present year, by whose di- rections it was put to experimental tests of a most severe character at Liverpool, under the direction of Commander BEVIS, R.N.

Two of the boats of the Baltic, one of the COLLINS' line of steam ships, were, by the courtesy of her Commander, Captain COMSTOCK, placed at Captain BEVIS'S dis- posal on the occasion. On one of them, a large boat, then lying keel uppermost on the steamer's deck, a strong man inflicted some 20 blows on one spot with a long handled axe, using all the strength he could muster, yet he was unable to make even an inden- tation; whilst every blow it is said would have told with shattering effect on a wooden boat.

Another, a smaller boat, was then taken ashore and rolled and tossed about on the rough cobble-stone pavement with all the strength of 6 men; then lifted up many times on end, and suffered to fall with great violence on the stones without any injury being done; she was next launched and rowed several times stem on to a stone pier, with all the power of 4 men, but no leak or injury was produced. Yet these boats had been five years in constant use on board the Baltic without repair.

After the receipt of Captain BEVIS'S re- port, the Lords of the Admiralty ordered * The " Metallic Army Plateau" in the accom- panying page of diagrams shows another form in which this material has been made available in the United States.

two men-of-war's boats for further trials.

These boats were, in June last, submitted to similar tests to those above related, and we are informed were in addition filled with large blocks of stone placed amidships, piled up to a considerable height, and then hoisted up with tackles at bow and stern; through all which rough usage they passed un- scathed.

As these important results have now been made publicly known through the lectures and pamphlet of Major EYRE, above alluded to, and again more recently in a paper read by him before the British Association, at their recent meeting at Cheltenham, since published in the Journal of the Society of Arts, of Aug. 22, we cannot doubt that a full and fair trial will be given to the me- tallic boats, both by our ovvn mercantile marine and in the Royal Navy. Indeed, we are informed that steps are already in progress for the establishment of a manu- factory of them in London.

Although somewhat digressing from the subject of this article, we cannot conclude it without holding up for imitation the example of Major EYRE to our younger readers, especially if intended for the naval or mili- tary profession; for it is chiefly through his active and zealous exertions that the benefit of these apparently invaluable inventions are about to be conferred upon our country.

Major EYRE had come to Europe on the usual leave or furlough allowed to officers in the service of the East India Company, as a relaxation from their duties, and a means of recruiting their health, after lengthened ser- vice in a tropical and often unhealthy climate.

He, however, was desirous to devote this leisure time to some more useful and honour- able purpose than mere idleness, and eagerly embraced this opportunity to do so. It is much to be wished that every officer in our military and naval services was actuated by the same desire to seize such opportunities of adding to .his own professional knowledge, and of rendering service to his country, and thus to raise the standard of character and add to the renown of the profession to which he might have the honour to belong.