The vessels he alluded to were very seaworthy boats; and on one occasion, when on a voyage to Dublin, the Shannon, a large merchant steamer, had been obliged to run for shelter, one of these vessels had rode out the gale, and made her passage. He believed that they were propelled by Mr. Smith's screw, and that he could give all the particulars of their construction.

Mr. F. P. SMITH said the vessels alluded to were the Margaret and the Senator, trading from Hull. They were fine fourmasted schooners, of 242 tons burthen; each vessel had on board two engines, severally of 14 horse-power, placed as close as possible to the screw propeller, which was driven by gearing. The total weight of the engines, screw, and tubular boilers with their water, was 15 tons, and they worked under a pressure of 8 lbs. to 10 lbs. of steam.

In a trial between one of these vessels and the Shannon steamer, it was found that, between Dublin and London, the Shannon consumed 90 tons of fuel, while the schooner, with 300 tons of cargo on board, only used 18 tons of coal, and arrived in London within 10 hours after the Shannon. In an experiment with the Senator, with 172 tons of cargo on board, when steaming only, the rate through the water by the log was 6 knots; and with sails and steam the rate was 9 knots to 10 knots. It was remarkable that this increase of speed did not appear to augment the consumption of fuel; whereas with paddle-wheels and sails the consumption of fuel increased in proportion to the rate of the vessel through the water.

Captain HOSKEN could not permit the discussion to terminate without stating that in his opinion, as a naval officer, one of the great merits of the screw as a propeller was its capability of being adapted to a fullrigged ship, using at times her canvas as usual. The British seamen would thus be fully as much employed as heretofore, and they would retain that superiority which had so largely contributed to the high position held by Great Britain in the scale of nations.

Mr. J. FIELD, V. P., said he had received a communication from Lady Bentham, relative to some of the improvements in naval architecture, introduced by the late Sir Samuel Bentham, which appeared to be so interesting that, with the permission of the President, he would request a portion of it might be read to the meeting.

The communication commenced by stating that, as in the paper on the construction of the Great Britain, particular stress was laid upon the advantage of fixed water-tight bulk-heads, dividing the hold into several compartments, the merit of the first introduction of that great improvement in naval

architecture must be claimed for Sir S. Bentham: it then proceeded,

"On reference to his Naval Papers, it appears that in the year 1795, he was entrusted by the Lords Commissioners of the Amiralty to construct six vessels of war, according to his own ideas and under his direction, at Redbridge. In the Naval

Papers, No. 8, part 8, 'Improvement in vessels of War,' a short communication is given of the several expedients he introduced into them, with a view to strength, durability, efficiency, and diminution of cost; (page 91,) it appears that he had introduced in those vessels 'fixed bulk-heads, or partitions formed in a manner calculated to contribute to strength, both in the transverse and longitudinal directions; that they comprehended in their construction diagonal braces, at the same time that they served as partitions for the convenience of habitation or for the separation of stores;' that they connected the bottom, sides, and decks together, so as to prevent their racking or working at sea; that a farther use of these partitions was, that having been made watertight, as practised by the Chinese of the present day, as well as by the ancients, they tended to secure the ship against foundering, by confining the water from a leak to the space between two partitions.'

"Again, (page 99,) amongst the various expedients enumerated, as tending to diminish the danger of material injury or the loss of a ship in case of her striking the ground, it is stated, that "the interior of the vessel having, as above-mentioned, been divided into several water-tight compartments, it is not even the flowing of water freely into one or two of these compartments that would endanger the loss of the ship.

"So also in The Elements and Practice of Naval Architecture' (page 177, third edition,) in giving an account of the abovementioned vessels of Sir Samuel Bentham's construction, the author says, 'the mode of structure of these vessels is very different from that of others;' and after mentioning various particulars, says, but the principal strength seems to depend on the thwartship braces and bulkheads, which connect the sides together more conformable to the practice of civil architecture.'

"Besides these fixed bulk-heads, the metallic water-tanks (invented by Sir Samuel Bentham for the preservation of water), were, on board these vessels, 'so contrived that their fore and aft partitions, extending in height from the bottom of the ship to the deck, operated as supports to both bottom and deck.'-Naval Papers, No. 8, page 108. So also the metallic canisters for keeping powder were adapted to the shape of the vessel,'

"It may be added, that other of the improvements introduced, I understand, in the Great Britain, had, as well as the watertight compartments, been half a century ago exemplified in Sir S. Bentham's vessels; such as the tumbling-out of the topsides and the straight decks.

"The above-mentioned work, Elements and Practice of Naval Architecture,' and Sir S. Bentham's Naval Papers,' Nos. 2, 7, and 8, record the extraordinary strength and efficiency of his vessels, as well as a variety of peculiarities in their construction, whereby that strength was given, with about half the quantity of timber used in the customary mode of construction, and only onesixth part of the copper was used for fastenings.

"This statement cannot in any way detract from Mr. Guppy's merit in the construction of the Great Britain. Real genius disdains to appropriate, without acknowledgment, the improvements of others; thus Sir S. Bentham referred, as above, to the Chinese and to the ancients. Whether Mr. Guppy may have re-invented the expedients in question, or have perceived the advantage of them, as proved by the actual service of the vessels in which they were exemplified, and have adopted them, to him must be ascribed the benefit which shipbuilding cannot fail to derive from his introduction to general use, of Sir S. Bentham's improvements in naval architecture".*

* Since the receipt of this communication, the Secretary has received from Lady Bentham a paper; from which the following extract is made:-" It is now half a century since Sir Samuel Bentham, in conversation with the First Lord and other Lords of the Admiralty, satisfied them, that the general principles of mechanics were as applicable to naval as to civil architecture, although they never, up to that time, had been scientifically applied to the construction of ships. The consequence was, that the Admiralty induced him to undertake the construction of six vessels of war and a water vessel, in every respect conformably to his own uncontrolled ideas, and under his sole direction. These vessels were the sloops, the Arrow and the Dart, and the schooners, the Netley, Millbrook, Redbridge, and Cling; all vessels of war.

"These vessels differed, in exterior form from the general build of vessels of war, having been larger and sharper; they projected or raked forward above the water-line, like a wherry; the top sides, instead of retiring inwards, were continued flaring outwards to the upper edge. By this difference in form, the vessels were better supported than the usual ones, when pitching or rolling in a sea, and it was found that they both pitched and rolled easily. In actual service they proved excellent sea boats, sometimes keeping their station on an enemy's coast, when other ships of war were forced to run for safety; sometimes making their port when all other vessels on the same station were driven down channel; sometimes out-sailing vessels in company at sea. The Netley was the only vessel on the station that could be sent in-shore off Havre, in the night, because she was the only one that could be depended on for working off a leeshore in any weather, 'when they dared not trust

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Sir J. RENNIE, President, after expressing to Mr. Guppy the thanks of the meeting for the communication which had given rise to so interesting a discussion, said the construction of iron sea-going vessels was a subject of peculiar interest to the institu

the frigates.' To use the words of the 'Elements and Practice of Naval Architecture,' 'They have, generally speaking, been found to sail remarkably well; but in a head sea and tempestuous weather, their superiority as sea boats has been most decided.'

"For giving strength to these vessels several new expedients were introduced, such as

"In the construction of the vessel:

1. Diagonal trusses, or braces of oak, to prevent racking.

2. Fixed bulkheads, longitudinal and transverse, for fixing the bottoms, sides, and decks together. 3. Thick, strong pieces under the ends of the beams, in lieu of knees.

4. Increased thickness of the outer planking, and of the deck.

5. Straight decks fore and aft.

6. Placing the timbers at right angles to the rising line of the dead wood, instead of being all the way perpendicular to the keel.

7. Passing the beams between the timbers, so as to afford means of connecting the beams immediately to them.

8. Choice of timbers; namely, that of small scantling but well seasoned, by having lain long in the sap.

9. Avoiding the use of grain cut timber.

"In respect to fastenings:

10. Trenails of a shape of his invention, in steps, that is, of different diameters in different parts of their length, the greatest at their head, the least at their point, with conical heads engine-turned. These trenails held faster than the usual ones, yet the timbers in which they were inserted were less wounded than by the ordinary trenails.

11. The use of augers for making holes of corresponding exactness with the trenails, so that the holes might be perfectly filled up, to the exclusion of water and moisture. These trenails, so inserted, kept the planking of the bottom in perfect contact with the timbers, notwithstanding the most severe caulking.

12. Short metal screws, hollow in the thickest part, the heads of a shape for holding firmly, and more particularly for fastening the butt-ends of the plank.

13. Bolt nails of a mixed metal, of a shape and of a hardness that admitted of their being driven into oak or fir, without splitting the wood.

14. Instead of bolts, only clenched-on rings. A new description of bolt, with screws on the ends; nuts to screw upon them, and plates, both for screwing the nuts against, and for receiving the heads of the bolts. Thus the bolts were not only drawn more firmly at first, but they admitted of being screwed up more tightly, in case of shrinkage of the wood.

15. Nails of a new form for sheathing, having flat and smooth heads, and tapered only in one direction; of pure copper, instead of mixed metal; thereby not liable to contaminate the sheathing on remelting.

"Expedients against loss, by injury to the bottom, and against foundering.

16. Extra thickness of plank for the lower part of the vessel, as above mentioned; it having been 6 inches intead of only 3 inches, as usually employed.

17. Terminating the plank against the deadwood, so that the dead-wood, the lower part of the stern-post, or even the keel itself, might have been beaten off, without letting water into the vessel.

tion, as to one of its early members must be ascribed the merit of their first introduction.

The first iron steam vessel that ever went to sea was built in 1820-1 at the Horseley ironworks, near Birmingham. It was named the Aaron Manby, after the constructor; and being put together in the Surrey Canal Dock, took in a cargo of rape

18. Giving such a form to the rudder, that although the bottom part might have been beaten off, still enough would have remained to steer the ship by.

19. In the Arrow and the Dart, hawse-holes in the stern, the same as in the bows, to enable them to be brought to anchor in a narrow channel, riding stern foremost.

20. A pre-eminent improvement against foundering, was the water-tight compartments, first introduced in these vessels. That is, the longitudinal and transverse bulkheads, so efficient, as above mentioned, in point of strength, by being made water-tight, divided the vessel into several watertight compartments, so that, although water should have entered into two or three of these compartments, the vessel would not sink.

"Against accidents from explosion:

21. Instead of casks, metallic canisters for keeping powder. These canisters were air and watertight, and were so arranged, as that in case of alarm of fire, water might easily have been let in over and around them, without injury to the powder, and so that after the danger were over, they could speedily be laid dry again.

22. Safety-lamps in lieu of a magazine light-room. These lamps were encompased by a double casing of glass, filled in between with water; the whole so contrived, that in case of breakage of the glass, the water would extinguish the light.

"Expedients with a view to efficiency in point of stowage-room, and to the health and comfort of the crew..

23. Instead of store-rooms, against the sides of the ship, fixed bins, not higher than tables, were introduced, leaving a clear space around them, as well as above them, so that besides easier access to the stores, the sides of the vessel were left clear to get at them, to stop shot holes.

24. The powder canisters were adapted to the shape of the vessel; consequently a much greater quantity of powder would be stowed in a given space, than where the powder was in casks.

25. The invention of metallic tanks for holding water, instead of casks; with a view to the preservation of water sweet at sea.

26. The adapting those tanks to the stowage of a much larger store of water than usual. This was effected by forming them to the shape of the vessel, so that no space was lost between them and the sides, nor between one and the other of them, as necessarily must be in the case of casks. The framing of these tanks also contributed to the general strength of the vessel, by its extending from the bottom to the deck, and so connected to them, as to form a part of the general fabric.

27. Thick pieces of glass as illuminators, either flat or convex, were introduced in various parts of the vessel, usually dark, but where light was very desirable.

28. Greater distance than customary between deck and deck, so as to give height for the men to stand upright.

"The expedients introduced in these vessels with a view to economy in their structure, were"In regard to timber:

29. The use of small timber, of which there were

36. Screw-pointed bolts, whereby half the usual number of bolts was saved.

37. Sheathing nails of pure copper.

38. Bolt nails of mixed metal, instead of copper. "The efficiency of these expedients for their intended purposes was proved in the long and active service of these several vessels.

On

"In point of strength, they were exposed to a variety of severe trials without injury. Amongst others, the Millbrook, after launching, was left dry at low water near Southampton by some accident, across and hanging on a log of wood; her sheer was not broken, nor did she sustain any other injury. The Dart, in the year 1799, with her guns and stores on board, ready for action, on going up the Texel, with much smaller vessels, and where no other of her force and size dared venture, frequently got aground, and dragged and beat against the shoal, without being in the least injured. The Redbridge, of no more than 160 tons, yet carrying fourteen carronades, sixteen pounders, had one of them, by accident, loaded with three shot, together with the full charge of powder, and which was fired off without the least injury to the vessel. board the Dart, one of her thirty-two pounder carronades, was fired no less than eighty rounds successively, and with an expedition far exceeding what is possible with ordnance mounted in the usual manner, yet the vessel was not in the least affected by it. On the same occasion, the Cling fired four hundred round shot from her aftermost carronade, without doing the slightest injury on board. In many letters it was stated that, after storms and the roughest weather, not so much as the paint or whitewash on the seams of the six several vessels had been disturbed. On an official survey of the Dart, and this after she had been in service seven years, it is stated in the official reports of that survey, and amongst many other proofs of strength, I do not find one decayed timber in her; a circumstance exceedingly uncommon in ships of such an age. I do not perceive an evidence of even the pitch of the butts on the gangway having cracked. On the most minute survey, more than once or twice, I discovered not the least sign of working. The calking at the wooden ends was perfectly sound and good. The oakum in the seams was perfectly dry and solid; even the indents remain in it, caused by the sawn edges of the plank, &c.'

"It seems proper to add, that the Dart had been in many actions previous to that survey.

present Secretary of the Institution. The propellers were the feathering paddles, which were invented by the late Mr. John Oldham. Both the engine and the paddles had been superseded by more perfect machinery, and the boilers had been frequently renewed; but the hull of the vessel had required but little repair, and was still at work upon the Seine, as were several other iron vessels built by

"In respect to the expedients against foundering, besides the examples these vessels afforded, of their security after beating on the ground, it must be noticed that, since of late water-tight compartments have been adopted, striking instances have occurred of the preservation of life by this expedient.

"As to stowage-room, and health and comfort of the crew.

"The space gained by the above-mentioned and other minor arrangements may best be judged of by a comparison of that between decks in an eightand-twenty gun frigate and the Dart. In a frigate of 28 guns, taken for comparison, there were but 10,278 cubic feet between decks; whilst between decks of the Dart there were 19,306 feet; or in the frigate, 52 feet to a man, in the Dart sloop, 137 feet

to a man.

"The Dart and Arrow were of about 500 tons; but though carrying the number of guns of a 28-gun frigate, they had a sloop's complement of men.

"A much greater quantity of powder and of various other stores were stowed in a given space. The quantity of water was nearly double; and, what is of great importance in regard to this necessary store, by the invention of metallic tanks water can be preserved sweet at sea. A quantity of water, that had been no less than three years in one of the tanks on board the Dart, having been sent, in the year 1800, duly verified in every respect, to the Society of Arts, their honorary gold medal was awarded to Sir Samuel Bentham for this invention.-(Vide Trans. Soc. Arts, vol. xix. 1801. Pp. 191 and 374.)

"Metallic tanks have since been very generally adopted, with the difference in favour of those now used, that they are of the cheapest metal-iron; but on the contrary, they have usually the disadvantage of not being shaped to the form of the vessel, and of not contributing in any way to the strength of its structure,

"Saving of first cost.

"It appeared from the Report of the master shipwright of Deptford Dockyard, on comparing the quantity of timber employed for the Dart with that consumed for a frigate of the same size, the Maidstone, and taking into account, in both cases, the loss on conversion, that not a seventh part of that used for the Maidstone had been necessary for the construction of the Dart.

"The absolute saving in copper, together with that of the timber, was so great, that a contractor dealing with the Navy Board, and conversant with the structure of these vessels, made a direct offer to that Board, to build a frigate, according to this new mode of structure, for little more than half the price paid for vessels of the same magnitude, according to the usual mode.

"In addition to the improvements exemplified in the above-mentioned vessels, may be specified, Sir Samuel Bentham's invention of 'Coqueing.'

"This mode of connection, he described, as applicable to framed work in general, in all cases, where the force to be resisted tends principally to make the pieces slide one over the other. It was particularly noticed and approved of, by the Lords of the Admiralty, on their visitation of the Dock Yards in the year 1802.

"The most important advantage of this invention, is the very great additional strength given to ves

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Mr. Manby, about the same time, at Horseley, and at his works at Charenton, near Paris.

The introduction of iron, as a material for ship-building, was now becoming so general, that the result of the great experiment, the Great Britain, must necessarily be regarded with much interest, and next session, the Institution would look forward to receiving from Mr. Guppy an account of the first few voyages; and, if skill and experience could accomplish them, they might be considered safe in the hands of Captain Hosken, whose success in the Great Western had been so decided.

ELECTRIC LIGHT IN MINES.

Sir,-Allow me to correct an error into which your correspondent, Dr. Cormac, has fallen in regard to the employment of electric light in coal-mines. Although he considers it unnecessary to go into the details of the subject, he could not do anything which would have been more to the purpose; for the electrician well knows that the light cannot be applied to any practical purpose till some method is discovered of rendering it continuous or constant. When a light is produced from charcoal points, they are volatilized with rapidity, and destroyed. To illustrate this, I will mention one of the numerous experiments I have made in endeavouring to overcome this difficulty. When a powerful Grove's battery of forty pairs was employed, pencils of that hard and very incombustible coke found in the inside of gas retorts were consumed at the rate of from half an inch to an inch per minute, and that too in a glass globe filled with nitrogen gas, and thus entirely excluded from the oxygen of the air. Wood -charcoal is volatilized much more rapidly. The attempts made at Paris and elsewhere have been entirely defeated by this obstacle; and indeed there does not seem any way of overcoming it,

sels, of which the parts are so combined. Besides this, savings are effected by it in various ways; by the saving of timber, for instance, where coqueing is employed, instead of tabling, as in making masts, in which case the saving of workmen's wages alone, amounted to 25 per cent.; that having been the reduction made, on the price paid them for putting masts together, when this mode was introduced.

"This invention was soon very generally adopted by private ship builders, and has been used in some cases of civil architecture and engineering, to which arts it is equally applicable. The Ordnance Department also very soon adopted it."