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it is seen, when treating upon the law of lateral resistance, that when the model was drawn forward through the water, as well as sideways, the centre of lateral resistance, at the time, moved forward also; and the estimated proportion equalled one-twelfth the length of the model.

Let this result be compared with Nature's form. Take a model 28 inches long, its middle will then be 14 inches; divide 28 inches by 5, and the answer is 5 inches. Now two-fifths of 28 equals 11; and threefifths equals 163; and 14 minus 11 equals 3, or 3 inches, which is the distance before the centre of length where Nature places her greatest width in birds, and in the sole fish. With the model in Chapter III. one-twelfth was the supposed place before the centre of length where the centre of lateral resistance resided when the body was moved both forward and sideways. The proportion of one-twelfth will be found to equal 2 inches, and rather more; being certainly less than 3 inches. It was stated, however, that increase of the speed of the model would cause the centre of lateral resistance to move still more forward. If granted, the average, allowing for mistakes, will be somewhere not far short of Nature's distance of 3 inches.

If the above statement be admitted near the truth, it follows, that whenever the line of greatest breadth of beam in a ship be situated aft the two-fifths of length, so as to destroy the balance of three-fifths of stern length, the evil must be compensated for, giving an equivalent in extra depth of keel towards and at the stern. Hence, the further aft the midship section be placed, the deeper must the keel be made, to preserve the due proportions of perpendicular surface of the two-fifths and threefifths between the body before the midship and the body aft of the midship. Now, great depth of keel towards and at the stern is a serious evil in all ships destined for shallow waters, and is objectionable, in another point of view, as in respect of lee-way, on account of the greater power, from increased leverage, to overturn.

The forms of ships as regards beam to length, especially those for merchandise, should be regulated in a measure by the nature of the climate and sea in which they are destined to navigate. For, if to encounter stormy winds and seas, whose average continuance is above that in other climates and seas, their breadth of beam and angle projections ought to be strongly kept in view, and acted upon by the builders, to assist the stability. If, on the other hand, the winds and seas are comparatively moderate, less beam will be requisite, or greater length of vessel, and all angles dispensed with. Moreover, ships requiring much sail, in consequence of the breadth of beam, will need hands in proportion, to manage the same; which circumstance, being an item of increased expenditure, will ever have its weight with the owners of merchantmen. This does not apply, however, to men-of-war, whose hands are generally in sufficient number for all duties.

With the completion of these few hints, which have been derived from careful experiments, observations, and reflections, although upon a small scale, I now take my leave, sincerely hoping they will induce persons of far more competent abilities than I possess, to engage in making investigations upon a large scale, that the true principles of shipbuilding may no longer continue a mystery.

Successful Application of the Screw to a Ninety-Gun Ship, with Engines. By Messrs. JOHN PENN & SON.*

The Agamemnon, 90, Captain Sir Thomas Maitland, C. B., when she went down the river on Friday afternoon, made a speed of upwards of 10 knots per hour until she arrived opposite Purfleet, when some small part of the engine, which had been made of hardened steel, and too tightly fitted, became suddenly hot and set fast, which caused the breakage of an eccentric band. This slight damage was made good, and the corresponding part of the engine ground, so as to prevent the possibility of its heating, and causing a similar accident. After the accident she was taken by the Monkey and African steam vessels to the deep water below Gravesend, where she anchored for the night.

On the following day (Saturday) she raised her anchor and started at 1 o'clock P.M., having on board Captain Sir Thomas Maitland; Commander Hall, who had joined on the previous day; Mr. Lloyd, chief engineer of the steam department at Somerset House; Mr. Trickett, assistant to the chief engineer at Woolwich Dockyard; Mr. John Penn, Mr. Hartree, and Mr. Matthew, of the firm that constructed her engines; Mr. Whitworth, engineer, Manchester; and Mr. F. P. Smith. The Agamemnon, in a few minutes after starting, began to draw the Monkey and African steam-tugs through the water; and it was amusing to witness the greatly increased rapidity of the engines of the smaller vessels when they were drawn by the screw steam-ship. When the Agamemnon arrived opposite the measured mile in Seareach the time was taken, and she accomplished the distance in 6 min. 24 sec., or at the rate of 9.375 knots, and the calculation gave her an average speed of upwards of 10 knots per hour. As the Agamemnon proceeded onwards, her engines, of 600 horse-power, Messrs. Penn's patent trunk, worked in the most satisfactory manner, making 60 revolutions per minute without the slightest heating in any part. The cylinders of these magnificent engines are 78 inches diameter, equal to cylinders of 702 when the area of the trunk is deducted. The number of revolutions was from 58 to 60, or eight revolutions above the contract speed, and, notwithstanding this high velocity of engines of 3 feet 6 inches in stroke, not the slightest jarring in any of the fixed parts could be perceived, and the boilers supplied ample steam with moderate firing. The speed of the splendid screw steam-ship, drawing 17 feet 7 inches forward, and 20 feet 4 inches aft, propelled by a powerful screw of 18 feet diameter, with a pitch of 20 feet 6 inches, was the astonishment of all the captains and crews of the numerous sailing vessels coming up the river with the tide, and Mr. Stuart, the pilot of the Agamemnon, had a most difficult task to steer clear of them when tacking, as they thought they could cross her path in ample time, instead of which they had narrow escapes, and it was more owing to the excellent look-out of Mr. Bean, master of the Fisgard, and the care of the pilot, together with the admirable manner in which the engines could be stopped and set in motion, and the way in which she answered her helm, that her safe progress through so many vessels as • From the London Mechanics' Magazine, October, 1852.

were in the reaches below Gravesend was accomplished without the least accident.

On reaching the Nore, the Agamemnon's boilers got clear of the mud, in some degree, which had passed into them while working in the basin at Woolwich. She left the tugs several miles behind her, and the fast steam-packet Dryad, belonging to the Woolwich Company, was at that time upwards of a mile astern, being unable to keep up with her. The City of Canterbury, a fast boat, on her passage to Herne Bay, had great difficulty in keeping up with the Agamemnon; and although the former had her foresails up, the Agamemnon kept ahead in fine style for upwards. of three miles, until the City of Canterbury turned eastward for Herne Bay. Between the Nore and Mouse Lights, the speed of the Agamemnon was tried by Massey's patent log for half an hour, and found to be 10% knots, against a strong head wind, the engines making 58 revolutions, and the result was so satisfactory to Captain Sir Thomas Maitland and Mr. Lloyd, that they congratulated Mr. Penn on the success of the trial, which exceeded their most sanguine expectations. This fine vessel arrived and cast anchor near the Waterloo, 120, flag-ship at Sheerness, at half-past 4 o'clock, and all the officers and crews of the vessels afloat came on deck to witness her surprising speed. The Admiral's yacht Triton, came out to meet the Agamemnon, but was obliged to drop astern; although going at her utmost speed, the Agamemnon passed her, and she did not get into Sheerness till some minutes afterwards. It is understood that no further trial of the Agamemnon is considered necessary, until she is completely equipped and stored for sea. She is to mount a 10-inch gun on a traversing platform at her bows, and her other ninety guns will consist of long 32-pounders, of 56 cwt. each, and 32pounders of 42 cwt., and she has ample room to work them with effect, should their services ever be required. Notwithstanding all the reports of the high performance of the Napoleon, French screw steamship of the same class, and about the same size as the Agamemnon, but fitted with engines. of 1000 horse power, it is very questionable whether the Agamemnon will not, in all respects, equal her, although fitted with engines of comparatively much less nominal power, which do not occupy one-half the space, and probably do not weigh one-third of the Napoleon's.

Process for Imparting Greater Liveliness to Indigo-Blue in Stuffs. By L. GUILLOUET.*

This discovery consists in exposing the stuffs colored with indigo to the pressure of steam at an elevated temperature.

The blue coloring matter of the indigo is insoluble, and in order to fix it upon the stuffs, it is necessary to deoxidize it with green vitriol and lime. By dipping the stuffs into a solution of deoxidized indigo, a darker or lighter color is obtained, according to the length of the immersion.

Indigo is also of a volatile nature, and this is in fact one of its characteristic properties. It occurred to me, therefore, to turn this property to account, by exposing the stuffs colored with indigo to the action of a

From the London Chemical Gazette, No. 241

high temperature, under constant pressure in air-tight metallic vessels, strong enough to resist an internal pressure sufficient to act upon the molecules of the indigo to incorporate them with the fibres of the stuff, and thus produce a change in the physical constitution of the indigo.

The form of the vessels employed is immaterial, but they must be furnished with a safety-valve, and also with a cock, through which the atmospheric air may escape on the introduction of the steam.

The stuffs dyed with indigo are laid one upon another in the vessel in question upon a wooden pan, and enclosed in a cloth, which serves to prevent their coming in contact with the sides of the vessel, and also to absorb the moisture which is produced at the first introduction of the steam. The steam is then allowed to flow in at a pressure of from 2 to 6 atmospheres. After the lapse of about twenty minutes or half an hour, the cover of the apparatus is removed, and the stuffs taken out and left to cool, when they may be folded and packed.

This operation communicates a violet tinge to the color of the indigo, without in the least injuring the other true colors fixed on the stuff, which, on the contrary, become fuller and brighter. The web loses considerably in length in the operation, but the loss of breadth is scarcely perceptible; at the same time a thicker and finer texture and more body and softness are obtained.-Schweig. Gewerbeblatt, x1. p. 98.

For the Journal of the Franklin Institute.

The Reading Steam Forge.

We are pleased to record the opening of this establishment, which is creditable to the enterprise of our neighbors in Reading, and will doubtless be found highly advantageous to manufacturers in this and other cities. No locality can be found combining greater facilities for cheap execution of iron forgings, than the one selected for the works in question. It is in the midst of one of the richest iron districts of this State; and being on the line of the Philadelphia, Reading, and Pottsville Rail road, the great avenue for the coal trade of Pennsylvania, coal can be procured at a very low rate, while every facility is offered for the transportation of finished work to this city at all seasons of the year.

The main building is 260 feet, by 100 wide, and contains at present, three of Kirk's patent steam hammers (the heaviest weighing 26 cwt.,) intended for small work. For the heavier class of forgings, a Nasmyth steam hammer is now building, which is to have a five ton ram falling seven feet-one of the largest in the country. The company is also erecting a furnace and machine for the manufacture of locomotive wheel tires, a heavy shears and slotting machine, and a large lathe, (vertical,) suitable for boring heavy cranks, &c. At some future time it is intended, we believe, to put up a puddling furnace and rolls, so that all the processes of manufacture from the pig, will be carried on under the same supervision. The steam required for the engine and hammers is made entirely by the waste heat from the furnaces, over which the boilers are set. Coal brought direct from the mines, is deposited at the door by a branch from

the Reading road; and two other branch tracks traverse the building, so that a locomotive enters and is attached to the cars on which finished work has been deposited by the cranes. The economy resulting from these arrangements is obvious. The establishment is fully worthy a visit, as it combines the improvements made up to the present time in each department.

The New Patent Law of Great Britain. BY JOHN HENRY JOHNSON, Solicitor and Patent Agent.*

This act having already made its appearance in full, in many of our contemporaries, we think our readers will derive more benefit from a general statement of the changes which it effects, and the machinery through which it acts, than from a mere copy of the act itself. This is the more obvious to us, as the act is by no means particularly clear to the comprehension even of those most accustomed to the construction of the statutes; and it would be still more unintelligible to the majority of our readers, who do not probably number amongst them many members of the legal profession. Hence, the following translation may perhaps be found worthy of acceptation:

Commissioners.-The Lord Chancellor, the Master of the Rolls, the Attorney and Solicitor Generals for England and Ireland, the Lord Advocate and Solicitor General for Scotland, and such other persons as her Majesty shall appoint, are to be "Commissioners of Patents for Invention ;" any three of whom (the Lord Chancellor or Master of the Rolls being one) may act.

The commissioners are to have a seal of office, and are to make rules of practice, to report annually to parliament, and to appoint such clerks and officers as they may think proper.

Provisional Protection.-A petition, declaration, and provisional specification, very similar to the documents at present required on petitioning for letters patent, are to be left in the commissioners' office, and to be referred by them to one of the law-officers, who will have the power to call scientific assistance to his aid. If the law-officer approves of the title and provisional specification, both of which he can allow or require to be amended, he is to give a certificate of such approval or allowance, which is to be filed in the commissioners' office, whereupon the invention may, for six months from the date of the petition, be used and published without prejudice to any letters patent to be granted for the same. The entire expense of this proceeding, including agency, fees, &c., will probably amount to £10 10s. As the validity of the patent will principally depend upon this provisional specification, it will be necessary to frame it with the greatest care and consideration.

Instead of the proceeding last described, the applicant for letters patent may file, with his petition and declaration, in the commissioners' office, a complete specification of his invention; whereupon a certificate of the filing having been given him, the invention is protected for a period of six months, as before. Any letters patent granted, therefore,

• From the London Practical Mechanic's Journal, August, 1852.

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