The subject of my remarks, and to which I earnestly desire to draw the attention of your readers, of the public, and particularly of English engineers, is the merits and demerits of the two systems of engineering adopted in the vessels of the Cunard line, which have been built and manufactured in this country; and in those of Collins' line, the production of our brethren in the United States. Both are excellent in their way, and each, in the absence of the other, would have been-indeed has been -considered perfection; but competition, and a very proper and laudable rivalry, has shown which of them it is best and most desirable to adopt in extending Atlantic steam navigation.

They have shown this to a certain extent, but no more. Neither of these lines of steamers (as it respects their machinery) have developed the highest state of engineering knowledge now and for some time past existing in this country. Humiliating as it may be to British engineers to acknowledge that they are beaten, although by their next of kin, it is tolerably certain that we shall have to make that admission; and your intelligent correspondent in No. 1398, prophesies this: to the best of my belief this will be so, has been so, and it is capable of very easy proof why it should be so.

But, that it could not have been otherwise, I utterly deny. I assert, that means are known to us by which both these systems (and they differ but in small degree) may be immeasurably excelled, at a much cheaper outlay, diminished cost for repairs, both in engines and ships, and a far more efficient result in all respects; and that this is not only practicable, but has really become an acknowledged fact, it shall be my object to establish.

Steam engines are of various constructions and mechanical arrangements;-in principle, they are as left to us by the immortal Watt. Modern necessities and ingenuity have introduced many deviations from his plans, and, as might be expected from extended practice and experience, with good result. Mr. Watt left us the "beam" or "side-lever" engineexcellent in its way, and suitable to his time (it has many votaries even now); others have introduced the "direct engine;" others, tubular boilers in place of flue boilers; others, feathering or eccentric paddle wheels, in lieu of the common radial wheel.

Cunard's vessels possess none of these improvements;-they have beam engines, flue boilers, and radial paddle wheels.

Collins' vessels have beam engines and radial paddle wheels; but the boilers are partly tubular, and alone are the cause of their superiority over their competitors. This has been so ably shown by your correspondent already quoted, in No. 1398, page 402, that I do not think it either necessary or just to occupy your space with further proof than to observe, that the great evaporative power of the boilers, and the extended grate surface, (a capacity to consume fuel with economy,) must be conclusive to the minds of all professional men, and that all other things being the same, we must succumb. We must "go-ahead" again by merely availing ourselves of the means we possess, and we assuredly shall be triumphant in a superlative degree.

This is matter of grave import for the consideration of those whose pecuniary interests are connected with the Cunard line of steamers; it is

still more of importance to another great and flourishing Company, of whom I shall speak hereafter, but whose infatuation and error is so utterly unaccountable, when we reflect that they ought to be-must be-fully aware of the great advantages they might have secured by a more able and discriminating course, which, if taken, would have been the means of placing them at the head of the steam navigation of the world. It will be their ill-fortune to see the great mistake they have made in the spring of 1850.

It must be evident to all men that small space occupied by steam machinery on board ship, and its minimum weight, compatible with strength and efficiency, must be that which is to be desired. All modern improvement has tended to this end; indeed, diminished weight of machinery is really power, for thereby you decrease the immersion of your ship, lessen her resistance, and increase her velocity, with a greater capability to carry her cargo and make a voyage remunerative, without additional outlay

in fuel.

To do this to the greatest extent, there can be no doubt that we must adopt oscillating or vibrating steam engines, tubular or other improved boilers, and eccentric paddle wheels.

I have already remarked, that Cunard's vessels are fitted with the ordinary main lever engines, common flue boilers, and radial paddle wheels; the workmanship of the whole is excellent-in fact, it is a splendid piece of mechanism, and, of its kind, perfect. It has also been noticed, that Collins' vessels differ only in the construction of the boilers, which are partly tubular; and this, though but a small instalment of our knowledge, is still sufficient to establish a superiority, and therefore powerfully supports the position I have taken, and shall now proceed to make evident and patent to your readers.

The subject may be divided into the three portions already stated; namely, engines, boilers, and paddle wheels, and these I will take seriatim.

I. Beam engines are the most ponderous of all constructions now extant. I have before me a list of about 150 pairs of these machines, which, with common flue boilers and water, radial paddle wheels, and coal boxes, average about 23 cwts. per nominal horse power. The weights may be taken as follows, in decimal parts of a ton, and may be useful to many of your readers:

or just 23 cwts. per nominal horse power. I believe this to be an average weight of beam engines, &c., as detailed; but, if report be true, the machinery of the Cunard steamers weighs even still more; it is said to be 1000 tons! which, for 800 horses power, is just 25 cwts. per nominal horse!

The superiority of Collins' vessels does not arise from lighter machinery, but from the greatly enlarged evaporative power of the boilers, without increase either in weight or space.

Beam engines are very expensive to manufacture. Oscillating engines,

at £40 per horse, (boilers and paddle wheels being the same,) is a more lucrative order than beam engines at £50 per horse, which will appear evident when we compare the quantity of material in the two kinds of engines; they are more expensive in repairs, use more oil and tallow from the number of the parts, are subject to transverse strains, requiring an enormously strong and heavy bed-plate to counteract the pressure upon the main gudgeon, which has to resist double the force of the steam upon the piston.

It is also dangerous to work beam engines under heavy pressures of steam, unless the motive parts are made more than usually heavy and strong-generally 2 times the nominal power is the usual practice. I know one or two instances where three times has been obtained, but accidents have resulted, to which they will always be liable; but make the connexions as strong and heavy as you please, these engines can never contend in this respect with the direct or oscillating engine.

The space occupied in the ship is also of paramount importance. Beam engines of 800 horses power will require not less than 35 to 36 feet in the most important part of the vessel. Oscillating engines of the same nominal horses power will have ample room in 14 or 15 feet, and they require less than one-half the timber foundation or "sleepers" to erect them upon.

The oscillating engine is self-contained; all its strains are direct-not doubled (as in the main gudgeons of beam engines); a great number of parts are banished, and simplicity in its integrity duly obtained: the centre of gravity of the whole is lower, and therefore tending to increase the stability of the ship; the wear and tear is less, and, when requiring repair, the cost is small from the few working parts. It may be made to bear almost any pressure by a slight increase in the crank shafts and piston rods. It goes at once to its work, which it does with vigour and certitude-indicator diagrams fully proving a proper effect for every atom of steam that is used.

And, lastly, the weight of the oscillating engine is just one-half that of the beam engine. A pair of oscillating engines, properly constructed, (for we have quacks in engineering as well as in medicine,) will weigh no more than one beam engine.

Taking an average of upwards of 3000 horses power which I have designed, the engines alone weigh just 253 of a ton per nominal horse, or say 5 cwt. only.

Here, then, is a great secret, not so fully known as it should be; and I shall be amply rewarded if I succeed in convincing those of its truth who are so deeply and pecuniarily interested in this question.

It may be as well to insert here the weight of oscillating engines, tubular boilers, and mechanical wheels, which are as follows:

or just 14 cwt. per nominal horse! and this is not supposition, but what the writer has done with 3000 horses power, and what has been done by Penn for several years past in some of the finest of our men-of-war. The Retribution may be quoted, as one instance of the advantages to be obtained.

II. Tubular boilers have suffered much in reputation by being made too contracted in the water-ways, the tubes too close together, and the plates not sufficiently strong to resist the increased pressure used in them. They save both in weight and space, and are now designed quite free from the general objections made to them; they are not more expensive in fuel when a due proportion exists between the absorbent surface and the surface of the grates; and I know no reason why they should not be as durable as the ordinary flue boiler; they perhaps require more attention in blowing off, and keeping free from salt and earthy incrustation-that is all.

But the great saving is in the oscillating engine. If tubular boilers are objected to, we can have recourse to double tier flue boilers, which may be made with very slightly-increased weight and dimensions. The following Table will show the great improvements of late years in this branch of marine engineering:—

Therefore, making an allowance for the proper enlargement of tubular boilers for the purposes of ocean navigation, there will not be found any important preference over the double tier flue boiler.

III. Eccentric or feathering paddle wheels possess very important qualities; and although I adhere rigidly to the general opinions many years since expressed in print upon these wheels, as then constructed, they are now so much improved in manufacture and design as to have become commercially useful. They are nearly double the weight of common radial wheels, quite double the cost, and, so far as my experience goes, still give very great trouble and labor to repair. But for ships of variable draught, accustomed to contend with heavy seas, and also as conducive to the comfort of the passengers and crew, they are invaluable, and far beyond their extra cost; therefore I recommend their use for Atlantic navigation.

In a former part of this paper I referred to the Royal Mail Company (West India) who have lately entered into contracts to extend their fleet by the addition of five superb ships of upwards of 3000 tons displacement, having beams of 39 feet, and 270 feet long, drawing 19.6 when fully laden. I have already expressed my deep regret that this Company should

have contracted (with one exception) for the obsolete beam engine-flue boilers and feathering or eccentric wheels. This they will assuredly regret; but having, I trust, fully shown the advantages to be derived from another course, I will devote the remainder of this paper to show what the Company will attain, and what they might have possessed with a less outlay-how they might have secured the greatest perfection, and how they have left open an opportunity for a vigorous and successful opposition to their earnest and sincere desires to uphold the permanency of their enterprize.

They have contracted for engines of 750 nominal horses power; now, as I have already stated that beam engines at £50 per horse is not so lucrative an order as oscillating engines at £40 per horse, hence they might have saved,

750 horses, at £50 per horse,
750 66
£40 66

£37,500

£30,000

or £7,500 upon each pair of engines, or in the five ships no less a sum than £37,500, or just the cost of one pair of beam engines!

I need not say that the interest upon this amount is of some importance; or state the value of this sum as the nucleus of an insurance fund, and which this Company have hitherto found the use of in a more than usual degree. But the most important consideration will be the increased velocities of these ships, had they been fitted with machinery of the most improved and efficient kind.

I have already noted that their new ships are to have beams of 39 feet, and when laden and fully equipped for sea on starting from Southampton, are expected to draw 19 feet 6 inches of water.

The area of the immersed midship section will therefore be about 670 square feet.

We will also allow that the indicator power will be 24 times the nominal power, a very full proportion for beam engines to work safely under (unless they are made more than usually strong in the motive parts, as before explained.) We therefore have 750 x 2.5-1875 horses power.

It is well known by engineers that the power required to propel ships is as the cubes of the velocities, and from an extended experience, I assert that the mechanical result may be represented by the factor 800, and it will be perfectly correct to take the area of the midship section (in each case) as the exponent of the resistance of the ship. Therefore the velocity will be

This is, with beam engines of 23 cwt. per nominal horse power, or a total weight of 862.5 tons complete.

I have already shown that oscillating engines may be made to weigh but 14 cwt. per horse, and to exert three times the nominal power, without the slightest increase in the parts, and when so strengthened (an inexpensive process) may be extended to 33 times the nominal power. Therefore 750 x 14 cwt.=525 tons, or a saving upon the beam engine of 337.5 tons dead weight!!

The power of the oscillating engine will be 750 x 3-2250 horses, and