This

four rods were used to give additional strength lengthways. These were fastened at one end to a ring carrying the trunnions, and at the other to an iron plate, which they pressed against the breech end of the gun. Two of these rods and the trunnions are not shown in the longitudinal sections, but are seen in the cross-sections. gun was much stronger than necessary at the front part; indeed everywhere, except just round the seat of the charge. I regret, now, that I only fired it enough to prove that it was an efficient 18-pounder gun; had I continued till it burst, its strength relatively to service-guns would have been more definitely known. Being desirous, however, before injuring it to find out if a still thinner cast-iron core would suffice, I had this 18-pounder bored out to the size of a 24-pounder. Unluckily, in so doing the bore was not made in the centre, only half-an-inch of cast iron being left at one side of it. Even in this state, however, it bore, without injury, several hours' firing with charges varying from one shot and four pounds of powder, to one shot, two wads, and eight pounds of powder. It burst at the third round with the latter charge. This great strength was unexpected, the thickness of metal round the charge being only 24 inches; whereas, in a service 24-pounder it is upwards of 6 inches. My gun, too, had much less windage, It weighed 15 cwt., less by 5 cwt. than the reamed-out 24-pounders which are used with a service-charge of 2 lbs. 8 ozs. of powder. The iron service 24-pounder for an eight-pound charge weighs 48 cwt.

The next experiment I made was to get a 9. pounder service-gun turned down cylindrical from the trunnions to the breech, and on this part to place wrought-iron tubes nearly the exact size and weight of the portion of metal removed, but just the necessary fraction of an inch smaller. The wrought-iron tubes had dove-tailed flanges, so that the one clasping the other gave some longitudinal strength; not that I think this was necessary. Indeed, if outer tubes had been placed merely half-way to the trunnions, strength enough would have been attained. This gun was fired as follows:

2 rounds with 8 lbs. of powder and 2 shot.

lettered C, Fig. 2, is a roller-path, with a cam rising in two places. Rolling upon this is a wheel at the end of the crank lever D, which, by means of a short connecting rod, imparts motion to the lever E, which is fitted with a pawl playing upon a small ratchet, which is fixed upon a shaft, and thence by the inclined spindle F to the upper wheel, which, working in a rack, feeds down the drill; by this means the cut is given at both ends of the traverse. The handle G is used for working the inclined spindle, when required, by hand. In front of the bed or frame is fixed an adjustable table, similar to those used in the ordinary shaping machines, with adjusting screws for elevating or moving it horizontally so as to bring the work into its proper position. The spindles for this purpose are shown by the letters H and I. The upper chamber of the standard supporting the drill spindle is used as a receptacle for oil to be fed down to the cutting edge as required. These machines are often made longer in the bed and fitted with double standards, so that the operation can be carried on at both ends of a piece of work

at one time.

Fig. 4 shows examples of two applications of this new system of work. The first is the stump end of a connecting rod and the strap showing the slot holes as also the transverse opening, all of which can be formed in this manner. Next to this is shown a pair of forked ends forged together in the solid, and these, when slotted out by the traverse motion, present the appearance which is shown by the letter 4; they have after this to be merely divided, and the holes being drilled through, to be rounded in the

shaping machine. The formation of keyways in crank and other shafts, and oil channels in brasses, &c., are amongst the many applications of the traverse drill. When the traverse is not needed the machine can be used as an ordinary vertical drill, so that it is an exceedingly useful tool in the engine and machine shop, and will, we doubt not, ere long entirely do away with hand labour for the purposes for which it is adapted.

THE MANUFACTURE OF CANNON.

By Captain BLAKELY, R.A., M.R.I.A., F.R.G.S., &c.

My first experiment was to shrink a heated wrought-iron ring over one of cast iron. The result was the compression of the latter to an extent I by no means expected, the wrought iron being only slightly expanded. When separated, both tubes regained their original size.

I next made an 18-pounder gun, formed of a tube of cast iron, 51 inches in diameter, and 1 inch thick, over which were shrunk, side by side, short cylinders of wrought iron, the thickest of which was 2 inches. To resist the force of the ness where strongest of only 3 inches; that of a gunpowder, therefore, this gun had a total thickservice cast-iron 18-pounder being upwards of 5 inches. Yet the lesser thickness was quite sufficient, even though the initial strain, calculated as roughly approximated. As a cast-iron tube, 1 necessary on the outer tubes, had been but very inch thick, was insufficient to resist the longitudinal strain, and as the wrought-iron cylinders were not joined, but merely placed side by side,

From a paper read at the United Service Institution.

86

26

3 4

1

A cast-iron service-gun, of about the same size and weight, was fired, round for round, with this gun until the 110th round, with six pounds of powder and two shot, when the cast-iron gun burst. The superiority of mine was so evident, and a 10-inch gun made almost on the model of it. that Her Majesty's Government had a 68-pounder The 68-pounder made in 1857 will, I hope, be tested this year or next.

My fourth gun was an 18-pounder. The inner cast-iron tube was only 1 inch thick, and open at both ends, the breech being closed by a plug. This was decidedly a mistake, throwing too great a strain on the four longitudinal bolts with which this gun, like my first, was provided, though these are not shown in the figure. Over the castiron tube I put two layers of wrought-iron tubes; the first broad, thin tubes (five-eights of an inch making the two layers break joint, additional thick), the outer ones thicker and shorter. stiffness was obtained. This gun was firedround with 6 lbs. of powder, 1 wad and 1 shot

By

each was two five-eights inches thick-the four At this round the four bolts gave way, although united being equal to a solid bar the size of the

bore of the gun. The rest of the gun was uninjured, so that this trial was a great success so far as the method of obtaining lateral strength was concerned, the sides being at the thickest part only three five-eights inches thick. The charge which broke this gun was twelve pounds of powder -double the service-charge for guns more than double the weight, and four times the service charge of the 21-cwt. service gun. I had this gun remade with four bolts of the best charcoal iron; but they, too, broke, without injury to the tubular part. Though so far most satisfactory, this result made me decide not again to leave the entire longitudinal strain to be borne by outer bars

Shortly after I had taken my patent for cannon (February 1855), Mr. James Longridge took one for making hydraulic presses on the same principle. To test it he had some small brass cylinders cast, one inch in diameter and one-tenth of an inch thick. Round these he coiled steel wire with atension calculated to make each share in the work. When filled the cylinders could each contain 300 grains of the strongest sporting gunpowder. He put a certain portion of gunpowder into these, then at each end placed a copper globe, ground to fill up the aperture accurately, with the exception of a small touch-hole. The whole was then bound together by a strong wrought-iron strap, the section of which was about 2 x 11 inches, and the balls keyed tight up to their seats by a jib and cottar. The powder was then exploded with results, from which he found that the same cylinder which, unsupported was bulged by 50 grains of powder, and burst by 90 grains, could bear the explosion of 200 grains when reinforced by four coils of wire, each only one thirty-third of an inch thick. The initial strain on each coil being so adjusted that each was equally strained with the greater charge. For this purpose the first coil was put on with a slight strain, the next with a greater, the third with a greater still, and so on.

My fifth gun, which I made in 1856-those I have mentioned having been made in 1855-was a 12-pounder. The longitudinal strain I divided between four bars, attached as in former guns, and the cast-iron central tube which took half this strain, its breech-end, to insure this, having an aperture only half the size of the bore. This gun had two layers of wrought iron cylinders. The manufacture of this gun showed me the great uncertainty of the result of shrinking heated iron tubes. Those for this gun had been made of the same iron, carefully bored to the same diameter, and heated equally; yet about two feet in front of the breech they had compressed the cast-iron Mr. Longridge next experimented with cast-iron core so much more than in other parts, that the cylinders, one inch in diameter and one-tenth inch bore was there's th of an inch less. This determined thick, but close at one end. The other he secured me in future always to force the outer tubes on much in the same way as in the brass cylinders. cold, making the outside of the inner tube a little When filled these cylinders could hold 305 grains conical tapering towards the breech-end. Great of powder. They were strengthened with ironaccuracy can thus be obtained. Indeed, the wire coiled on with the requisite increasing tenmethod of heating and shrinking on the tubes Ision. With eight coils of No. 21 iron wire, had only adopted as a cheaper makeshift for the then, it appeared that these cylinders could bear first few experimental guns. Knowing from the explosion of 95 per cent. of as much gunpowder former experiments that it would be useless to as could be put into them. To find if it was the attempt to burst this gun with ordinary charges, material which gave this strength, and not the it being much stronger than any former ones, I method of making each part do its work, Mr. had long iron cylinders cast and turned accurately Longridge obtained a piece of the best wroughtto fit the bore. Unfortunately, I had too great iron, and made a cylinder similar to the others in confidence in it; and, instead of waiting a day or size of bore, but with sides twenty times as thick. This burst with a charge of 100 grains of powder. Mr. Longridge next made a three-pounder gun of a copper tube, with iron wire coiled on it. It was

two and having the compressed part again bored out cylindrical, I fired these closely-fitting cylinders from it. Having put in the powder for the fourth or fifth round, the cylinder was introduced, but stuck in the narrow part, and we could not get it out again. Thinking that the gun was too strong to be burst by gunpowder in any way, I fired it. It burst. Nothing could have been more injudicious than firing the gun so loaded. Not having any means of calculating the strain on it, nothing would have been proved had it remained sound. I should have been particularly careful, too, of this fifth gun, because I could not afford to make a sixth. This fifth gun proved nothing; but in all the others the increase of lateral, or rather circumferential, strength by my method of manufacture was great-indeed greater than I expected.

These guns had been made to test a principle, not as models. They would all have been too light for service except the 9-pounder. In No. VII.

meant to be fired with its breech abutting against some resisting substance; but at Woolwich they fixed it with the front flange resting against a piece of timber, and, of course, blew the breech off. To test the strength of this cylinder Mr. Longridge afterwards loaded it, buried it in the earth between two strong pickets firmly driven in, and fired the charge. It showed enormous strength. (To be continued.)

THE MAGNETISM OF SHIPS. By F. J. EVANS, Esq., Master R.N., F.R.A.S., Superintendent of the Compass Department, Admiralty. (Concluded from p. 44.)

IN the Royal Navy, as recommended by a scientific committee of truly eminent men some is adopted as a general principle: but a rigid years since, the system of no compensation

want of caution on the part of iron-ship construetors and those engaged in their equipment, evinced in the injudicious arrangements for the compasses given in the Liverpool Compass Committee's Reports. Among the instances quoted will be found the following: "The error in the first position of the binnacle was 101. As the ship was going to the East Indies, the compassadjuster objected to compensate so large an amount, and the binnacle was then placed three feet forward; here the error was reduced to two points. In another and much larger ship the compass in the first position of the binnacle deviated 14 points; on moving it a little further forward, the error was reduced to 24 points." These cases occurred when the original position was selected near the rudder-head of iron vessels, in which a strong attraction existed towards the stern.

The

It must be evident that under such circumstances of position no compass, whether compensated or otherwise, can possibly act faithfully, nor can any accurate theoretical deductions be made from such examples; nor, above all, need we be surprised at the serious consequences which too frequently result from dependence being placed these marvellous mal-arrangements. Liverpool Compass Committee acted wisely in the promulgation of a circular calling attention to these facts, and expressing their opinion that by attention to the circumstances under which a ship is built, and care in selecting a suitable position for the binnacle, the original error of the compass may be reduced within small limits.

on

Any observations on the theory of a ship's magnetism would be incomplete without reference to Mr. Airy's method of compensating forces, based as it is entirely on the laws which have been referred to, that is,—

At any place the deviation of the compass in any ship, whether wood-built or iron-built, may be accurately represented as the effect of the combination of two forces, of which one alone would produce a disand the other alone would produce a disturbance folturbance following the law of polar-magnet deviation, lowing the law of quadrantal deviation.

compass may be accurately corrected by well-known Consequently, at any place the deviation of the mechanical methods; namely, by a magnet in the athwartship direction, fixed at a distance determined by trial, for correcting the deviation when the ship's head is north or south; by a magnet in the head-andstern direction, also at a distance determined by trial, east or west; and by a mass of unmagnetised iron, at for correcting the deviation when the ship's head is the same level as the compass, in the athwartship line or in the head-and-stern line, according to circumstances (usually in the former), also at a distanco determined by trial, for correcting the deviation when the ship's head is N.E., S.E., S.W., or N.W.

For the same ship, the mass of unmagnetised iron, if adjusted at one port, will produce its due effect at all parts of the world, without ever requiring change or adjustment. The quadrantal deviation may thus be accurately corrected without difficulty, leaving only the polar-magnet deviation uncorrected.*

Mr. Airy's later investigations have led him to

tution, page 323, I have given drawings representing the proportions and the method of manufacture I would recommend for large guns -to throw a ton of iron, for instance.

I will here give a drawing of an 18-pounder field and siege gun I should like to see supersede the 38-cwt. gun now used. This gun would have double the strength, would cost less originally, and, weighing only 22 cwt., the transport would require fewer horses. Only the breech-end would require the strength of the double tube; but for some purposes it would be well to have a few guns made as light as possible. In these the principle should be applied the whole length of the gun. By using wire the weight of an 18-pounder gun could with safety be reduced from 38 cwt. to 8 cwt.

the compass

as free from error

as circum

The mercantile marine adopts more generally the system of adjustment, and this has led to the introduction of various patented compensating plans, differing widely from the Astronomer Royal's views, based often on no theory whatever, ending frequently in failure, and thus weakening the confidence of the seaman in the compass, and leading him to consider that the magnetism of an iron ship is so capricious as to be beyond all laws and all remedy.

compensation under all conditions, and whether its delicate and important manipulations can b entrusted to all classes of navigators. On one point, however, mariners may be assured, that at present no other method of compensation has been brought to their notice that has been more elaborately worked out by high scientific and philosophical attainments, or could equally stand the test of such profound mathematical analysis, as has been brought to bear on the subject by the Astronomer Royal.

See Philosophical Transactions for 1855, Art. V., Discussion of the Observed Deviations of the Compa-s

BUILT IN ENGLAND, WITH THE DIP OF THE NEEDLE FROM ES TO 70° N., PREVIOUS TO BEING LAUNCHED, ACCORDING TO THE LATE DR. SCORESBY.

TASK-WORK v. DAY-WORK IN THE
DOCKYARDS.

A FEW years since the system of day-work was ignored, and the public press was rampant in its censure, demanding task-work in order to satisfy the country that a fair day's work was obtained for a fair day's money. Task-work was therefore introduced, and in the course of a short space of time the most magnificent fleet that ever swam was fitted out from the Royal Dockyards; and where is the individual whose heart did not throb with delight on witnessing the departure of that fleet from Spithead in the late war with Russia ? These ships were the strongest that ever floated; were built with the strictest regard to strength and economy; and the workmen employed were paid from schemes of prices requiring very nearly "double" the amount of the work done for money in the private dockyards, resulting in the fact that whilst by these prices the men of the dockyard got at the rate of 5s. 6d. per diem., those in the merchant yards, on the gun-boats and other vessels, were receiving from 9s. to 15s. Merchant builders were encouraging men of the dockyards to enter their service-making choice of them before others to work for them.

Finding job-work to the advantage of the employer, shipbuilders would have introduced it in the merchant service, but the men of the union inform us that they protested against it as oppressive in many cases, in consequence of the estimates and contracts being taken low, then underlet, and, consequently, the men ground down. Task and job-work now receive the censure of those disposed to find fault, and object to restriction, and there is a disposition for change, though it is found that whilst the people on task-work get 5s. 6d. per day as earnings, the work is done at one-third less expense than by employing the people on day-pay-at 4s. per day. Job work is nothing more than payment of so rauch for building the ship, whilst task-work proviles for the various jobs distinct in building. To

* See page 42 in last Number.

RESULTING FROM ACTUAL EXPERIMENT, AS DE TERMINED AT LIVERPOOL BY THE COMPASS COMMITTEE, 1856-7.

BŒOTIA.

Built head to South (a little West.)

CITY OF WASHINGTON. Built head to North.

SARAH PALMER.

Built head to East (a little North.)

BORYSTHENE. Built head to N.E.

BARCELONA. Built head to S. W.

P

NOTE. The letters Pand S denote the port and starboard lines of no deviation.

the secretary to the Admiralty, but give a trial to the preceding suggestions, economy will be setunity given for those who have been calumniated cured in the public establishments, and an opporto prove themselves up to the mark. PHENIX.

TRIALS OF MOWING AND REAPING MACHINES AT WARWICK. THE mowing machines were tried upon a piece of grass belonging to Mr. B. Dickinson, Goy Brook Farm, not far from the town of Warwick. The crop was rather light. There were three mowers in the field-Burgess and Key's, Wood's (American), and Harwood's, which we alluded to in our account of the Ipswich Show. It was soon evident that Mr. Harwood had little chance of competing with either of the other two, for his machine left patches here and there uncut altogether; and when it did cut, the lowest sweep it was capable of making left much too good a portion of the grass upon the ground. Wood's did much better; but that also left occasional patches, and could not cut uniformly, and sufficiently low, so as to secure the greatest bulk and the sweetest portion of the crop. We entertain the same opinion as we have already expressed, as regards the grass-cutting powers of this machine. The mower of mowers, at least as far as we have yet seen, is that belonging to Messrs. Burgess and Key. There is no mistake about its effective working power; it goes into the crop, no matter how laid or trampled upon, and cuts it, to speak in familiar phrase, as close and as clean as a razor. This fact was evident to every spectator in the field, many of whom closely examined the ground, and most of whom, who had any practical knowledge of such matters, expressed themselves in the highest terms as regards the power of the machine. The saving in the crop of even moderate weight and extent, when cut by a mower like the one we have briefly alluded to, would therefore nearly pay for the first cost of the machine. As a proof, moreover, of the opinion entertained by the owner of the field as to the merits of the machine, he requested Mr. Burgess to cut the remaining portion of the crop, to which he acceded; and wo Mr. Dickinson to Messrs. Burgess, in which he exhave since seen a copy of a letter, addressed by

have vessels built substantially, let there be a greater number of foremen made who can watch the operation of the works, and then task-work is the best for the service. Let the Admiralty call a committee of the superintending measurers of the various dockyards together, and from our personal knowledge of them it will be found that an amount of invaluable information will be col-presses his high satisfaction at the manner in lected. It was the saying of an old master ship- which the work was done, and gives a practical wright-"If you want your work done have task-proof of his convictions being well founded, by work; if you don't want it done have day-securing for himself one of these mowers.

work."

There is another very important matter to be considered. The master measurers of the various

The reaping was upon a piece of green oats, and did not furnish any very satisfactory results as to the relative power of the machines. Tho crop cut belonged to Mr. Woodwards, and though yards have an important trust committed to them. it was heavy and much laid in places (supposed to They are responsible for the proper discharge of have been purposely trampled down to baulk one the whole of the duties of the office-to see that of the machines), the best reaper did its work the thousands of pounds weekly of the public very well. Messrs. Burgess and Key's well-known money are properly expended, and the work done machine cut down some of it in the condition in a workmanlike manner; and yet their pay is just described, about one acre and a quarter, and but £180 per annum, whilst there are those ap-left the ground very clear of the green corn. The pointed to do the secondary duty of dividing the others did their work very fairly, considering all money for payment who have salaries of between things, the nature of their construction, and the £300 and £400 a year, with others to assist at the difficulty of handling so unfavourable a crop. If ever there was a mistake this is However, it was a mere experiment, got up to one, and we hesitate not to say, that with proper amuse the visitors, more than to show the working organization £20,000 per annum of the public power of the reapers. Not so as regards the money may be saved through the instrumentality mower. Everything connected with that machine of task-work. Give support to the master measuwas serious and earnest, as regards its work; and rers, and pay them for their responsibility; and seeing that they have a very great responsibility a silver medal was awarded to it.-Bell's Week y so well did the Society appreciate the mower, that to sustain, give them a first instead of a subordiMessenger. nate position. Now they can be snubbed and be dumb; give them their due importance, and silenced in the face of injustice, and compelled to justice will be secured in every respect to the

same rate.

country.

It may be added that if there is any doubt yards and the private establishments, we know about the difference between men in the Dockand affirm that the former are by far the best and

most substantial workmen.

Mis-statements have been made in the House of Commons that will be confronted, and if His Grace the Duke of Somerset, with the noble lord

RIFLING LARGE CANNON.

TO THE EDITORS OF THE "MECHANICS' MAGAZINE." GENTLEMEN, Captain Jervis, R.A., in his place in Parliament has asserted that it is impossible to rifle large cannon. I will undertake to throw an elongated iron or steel shot, poised on have a sixty-eight pounder rifled, which shall wooden wings to prevent injury to the interior of the gun, and of between two and three diameters of the bore of the gun in length, and undertake, also, to fire two such rifled cannons instantaneously by percussion, after the manner