of the results of these trials. I must now in turn do my part to reverse the result of the only one trial which the advocates of the paddle desire to see stand; viz., the 11th, head to wind against the gale. I have already stated, that the steam of Alecto on this trial was frequently at a pressure beyond what her valves were weighted to. She never wanted it throughout, while the reverse was the case in the Rattler. It was so with her at the first starting of the two ships at daylight in the morning, and though, when the signal was made, the Rattler was two cables length a-head of Alecto, she was very speedily passed, and the latter half a mile a-head. The Rattler's steam power gradually improved; her revolutions increased from 19 to 22, and, as this took place, she steadily came up with her rival, and at 8 hours 20 minutes, A.M., the trial having commenced at 6 hours 4 minutes 30 seconds, and the ships were abreast; when the Rattler's engines were rolled out of gear, and in the delay in getting them again to work, and getting head-way on the ship, Alecto regained her advantage. By 11. 30 A.M., the Rattler was again alongside of her opponent; but all exertions to keep steam proving fruitless, she gradually lost her position, and at 1 P.M., when the trial ceased, was one-third of a mile astern of Alecto. Now, of such a trial I would first observe, that looking merely to its final result, had it taken place between Alecto, Prometheus, and Polyphemus, (Rattler's three paddle sisters,) a similar difference in position between all three at its close might well be expected, and yet could never be urged as conclusive of inferiority in either ship; on the contrary, on such a result, after such a struggle, in such circumstances, the remark from all impartial and able minds would be to the effect, that a very close equality between them had been displayed. Why, then, upon such minds should even the bare final result in this case, as I have above recorded it, be permitted to weigh to the prejudice, not of a single ship, but of a most important principle? But looking at this trial in its circumstances as well as its result, and at the bearing of the one upon the other, I hold that it affords most conclusive grounds for supporting in this as in every other particular, the claim of the screw to that perfect equality of power for which I plead. First, the gain of the Alecto on the Rattler (except for the last hour and a half, when the latter's steam was gradually falling) was in every case sudden and rapid; while the gain of the Rattler on Alecto was in character steady and constant, and occupied in its periods by far the greater time of the trial. And, secondly, putting aside the inequality in their circumstances as regards steam, had it not been for the accident to her paddle engines, it is clear the result of the trial must have been reversed. The speed of both ships by patent log was 4.2 knots, and the 8 minutes of time lost to the Rattler in starting her engines again, and gathering head-way against a heavy gale and sea, enabled Alecto to take the lead by half a mile. This advantage by 11.30 was again taken from her, and but for the accident, this half a mile gained by the Rattler from astern to abreast must have been gained from abreast (where the accident took place) to ahead; and would more than have compensated for the loss of the one-third of a mile, which she subsequently sustained on losing her steam. I have been thus prolix on this trial, because, as the only one of the nature ever yet made, its bare result has been used as the means of prejudicing the public mind against the equal power of the screw with the paddle to contend with bad weather. This prejudice it is the open object of the above statement to remove; as it is of the following one to do the same by the grounds on which it is supposed to rest. It has been speciously asserted, that the cause of the screw's inability to contend with heavy seas is to be found in its loss of power when the ship pitches-such assertions going even to the extent, that it is thus at times pitched out of water. To these assertions the screw-shaft itself shall supply the most unequivocal contradiction. The lowest amount of pressure it ever made in any of these trials, in any weather or sea, for the many hours of each in which it was kept acting on the dynamometer, and its efforts registered, were equal to 1 ton, 16 cwt., 3 qrs., and this minimum on pitching was immediately connected with, and followed on the accompanying ascending, by a maximum thrust amounting to 5 tons, 5 cwt. The mean pressure of the shaft, taken over an hour of the period, when the above extremes were registered, was 4 tons, 2 cwt., 2 qrs., 23 lbs. In every case of increased re THEIR COMPARATIVE POWERS OF SPEED. sistance to the ship, from whatever cause, an increased pressure from the screwshaft helped her to meet it; the greatest resistance to the ship being accompanied with the greatest pressure—and the least with the least. And as regards resistance from the state of the weather, her highest speed in the trial of smoothest water was produced by a pressure of 3 tons, 17 cwt., 3 qrs., 14 lbs.; the lowest speed in the strongest gale and heaviest sea, by one of 5 tons, 3 cwt., 1 qr. And now with the view to confirm the justice and truth of the charge, or on the other hand to exhibit the utter groundlessness of the general suspicions and misapprehension which obtain on this important point, I here openly invite any officer or gentleman, who is in possession of undoubted testimony, whereby he can substantiate against the screw a greater loss of power than is found in the paddle, when fairly it has been tried against heavy weather, under fair circumstances, and on a practically large scale, to come forward and submit that testimony openly before the public. To that public he is in justice bound to do so; that to himself he is in justice bound to do so, as well as to the principle itself, whose true character he may thus establish before the world. I make this invitation, however, with the fullest confidence that it will nowhere find acceptance; and in proof of that confidence, I here take the liberty of appealing directly to those able and talented gentlemen, the heads of our large engineering and large building establishments, by whose influence and judgment the public in these matters are so largely and properly led, whether by direct experience of their own, or by unquestionable evidence from others, they have ever known a single case where, under such conditions as above, such supposed inferiority has been displayed. And further, if, as I feel well assured is the case, no such conclusive evidence has ever yet been brought before, or known by, any one of them, I then trust that, in the exercise of a just and honourable candour, all doubts and misgivings wherever entertained on the subject may be at once dismissed; and that, as resulting from assertions and insinuations as little in accordance with reason as with fact, they will be no longer permitted to prejudice in their minds a principle so important and so hopeful, and deprive the public at the same time of 369 practically reaping the many advantages which its employment holds out. The trials with the Alecto were over; but the confidence produced by their result induced the Admiralty to permit the powers of the Rattler to be tried against those of the Vesuvius,- -a ship of 970 tons, and 280 horses power, with a proportion of tonnage to power of 3-4 to the Rattler's 44, with new boilers; ship and engines thoroughly repaired, with a clean bottom, prepared and fully equipped for a three years' commission, and having always had the character of a fast ship. Here at least were no advantages allowed or taken by the screw. Both ships, at their load draughts, left Greenhithe together on Friday evening, to try their respective speeds as far as the Bass Rock,-the Rattler at once taking the lead. By her the Bass was rounded at 11 A.M., on a Sunday following, and returning on her course; after some time the Vesuvius was seen with a nice breeze, under steam and sail,, pursuing her way to the Rock. The sail was taken in, and the ships communicated. The Vesuvius had taken a course by which her distance had been lengthened 7 miles-for this an allowance of one hour was made; a further allowance of more than one hour was then made for the delay attending the communication; and the gain in time by the Rattler over Vesuvius, in steaming from Greenhithe to the Bass, was thus reduced from being more than 7 down to 5 hours. But that there might be no mistake as to the actual relative speed of the two ships, and that the paddlewheels might have the full advantage of nearly two days' consumption of fuel, the Rattler returned with her opponent to the appointed goal, and in the interval twice steamed round and round her. I have endeavoured to establish the claim of the screw to perfect equality with the paddle, whether in general or in special circumstances, by thus adducing the unquestioned testimony of the publicly recorded and particular trials. I shall hope to confirm that claim by now adducing the equally unquestionable testimony of the publicly recorded speeds of all her Majesty's armed steamers, whether loaded or light, as those speeds have been ascertained by that severest and most truthful test, a mean of runs made before the measured mile in Longreach, and APPLICATION of gunpowDER TO THE WORKING OF RAILWAYS, as those speeds are now found to stand in the public Registers. Now, as regards the position of the Rattler in the above list of loaded ships, it may be urged that the immersion of the screw in such cases is more favourable for good work than is that of the paddle, but that, as the ship lightens, the paddle itself will improve in work in addition to the decreasing resistance of the ship. The first part of this view I accept as being decidedly favourable to the screw, and with the second I have no desire to quarrel. The closest struggle between the two principles will surely occur at the period of best dip of the paddle. But I am looking at the question practically as it will occur in sea-going ships, consuming their store of fuel on their voyage; and on this view it will be seen that a period of worse work, when the paddles are too light, succeed to the period of most efficient dip, as a period of worse work when they are too deep precedes it. Both these extreme periods of inferiority are at least of equal duration with the intermediate one of superiority-two bads to one good, and together must cancel all reasonable expectation of its effect being such as to put the stamp of deficiency on the more constant and equable labour supplied by the screw; which as fully as its rival can, up to an extent, feels the benefit of the lightening of the ship, and the proper immersion of which may in all cases be longer preserved from the circumstance of the trim of the ship being able to effect it. Again, in the trials here shown, the Rattler may be thought to have been more nursed than her neighbour. To this I reply, that on all such occasions the best work is always endeavoured to be, and is procured from every ship. But to any with whom either of these objections can obtain any favour or weight, I beg to point to the very unfavourable extent to which (with exception of her sister ships) the Rattler comparatively is powered, as to a fact which must more than counterbalance in every candid mind any conceivable advantage she may be supposed in these comparisons to have derived from both of the above causes (even if proven) put together. I now most respectfully submit this letter and its contents to the especial, the calm, and the dispassionate judgment of those minds which are most conversant with the subject on which it treats, and most interested in it; and I close it, not 871 APPLICATION OF GUNPOWDER TO THE WORKING OF ATMOSPHERIC RAILWAYS. Sir,-Permit me, through the medium of your columns, to suggest the employment of an inflammable compound such as gunpowder, or the recently invented explosive cotton, as the means of producing exhaustion and condensation in the traction tube of the atmospheric railway -a purpose to which it seems applicable, and apparently may be adapted with safety, in the simplest manner, and at a cost infinitely less than any other mode hitherto proposed-no expensive stationary engines requiring to be constructed or maintained. During the explosion of gunpowder, or any similar inflammable compound, two effects, diametrically opposite, take place. First, a volume of gas is generated, exerting a powerful expansive force; and secondly, by the ignition and annihilation of this gas, a vacuum is produced, in effect the reverse of the former. These actions, when confined, are violent; but by apportioning the strength of the charge to the space in which it is exploded, it is conceived that its power may be so far controlled as to render it available for the purpose referred to. The construction by which this end is proposed to be accomplished, it may be difficult to describe intelligibly without diagrams; but the general principle may be understood by supposing a strong tube,-say, a foot in diameter, and ten or more feet long,-both extremities of which are closed by a valve, opening outwards at one end, and inwards at the other. Gunpowder being introduced into the tube, near the last-mentioned valve, in separate small charges successively, by means of any suitable mechanism, might |