engines been kept on ahead, the effect of reversing was to turn her through 90 from the position she would have occupied had the engines kept on ahead.

Experiments with the Steam Yacht Columba,' belonging to His Grace the Duke of Argyll, June 29, in Gare Loch, the weather very fine, with little wind.

The draught of the vessel was 10 feet aft and 8' 2" forward. She was fitted with a Griffith's screw 7' 1" in diameter and 12' pitch. The experiments were witnessed by Mr. James R. Napier and his son, Mr. Robert T. Napier. When the vessel was going full speed ahead (about 10 knots) the engines were reversed, and the helm immediately put to starboard; the vessel turned to starboard until her forward way was lost, the time between the reversal of the engines and the stopping of the ship being about 1 minute.

When the vessel was going full speed ahead the helm was set to port, and shortly after the screw reversed. The vessel turned to starboard at first, and then to port until all way was lost. The turning to starboard at first was the natural result of the helm having been ported before the screw was reversed.

In the trials on this ship no measurements were made of the angles turned through. The direction of turning, however, was the same as before, the reversing of the screw at once reversing the effect of the rudder.

In all three of these vessels, therefore, the same effect on the steering was produced by the reversing of the screw when the vessel was at full speed.

The importance of this effect may perhaps be best seen from the diagrams (Plate I.), showing the various positions occupied by the Valetta' and the barge compared with those they would have occupied had the screws not been reversed.

In these diagrams the directions of the vessels correspond with the actual measurements during the trials; the positions and distances travelled being estimated from the known speed of the vessels. It had been the intention of the Committee to use one of Mr. Napier's pressure logs in order to ascertain exactly the positions of the vessels during the trial, but this intention was not carried out.

Diagram 1 shows the courses run by two ships after the reversing of the screw until they had lost all way compared with the courses they would have run had they continued under full steam, the helm being hard to port.

A glance at this diagram is sufficient to show what a fatal mistake it must be when a collision is imminent to reverse the screw, and then use the rudder as if the ship would answer to it in the usual manner.

But perhaps, as regards collisions, the most important result is that shown in diagram 2-namely, the positions of the ships when they have not lost more than half their way, and when, as regards the distance run, the effect of reversing the screw is but small.

As is shown in this diagram, it appears that whether the reversing of the screw reverse the action of the rudder or not, the rudder is nearly powerless to turn the ship, and that she will turn not only more rapidly, but in less room when going full speed ahead.

Before closing their Report, the Committee desire to express their thanks to the Earl of Glasgow, the Clyde Navigation Trust, and His Grace the Duke of Argyll, for the use of their vessels, and to the officers and crews who assisted in making the arrangements and conducting the experiments.

On the Investigation of the Steering Qualities of Ships.
By Prof. OSBORNE REYNOLDS.

[A communication ordered by the General Committee to be printed in extenso.] THE primary object of using steam power in ships is to enable them to pass quickly over long distances. Under normal circumstances rapidity and certainty in manoeuvring are matters of secondary importance; but circumstances do arise under which these powers are of vital importance. Experience has taught those who go down to the sea in steam-ships that their greatest danger is that of collision; and fogs are feared much more than storms. That there must always be danger when long ships are driven at full speed through crowded seas in a dense fog cannot be doubted; but this danger is obviously increased many fold when those in command of the ships are under the impression that a certain motion of the helm will turn the ship in the opposite direction to that in which it does turn.

The uncertainty which at present exists in the manoeuvring of large ships is amply proved by the numerous collisions which have occurred between the ships of our own navy while endeavouring to execute ordinary movements under the most favourable circumstances, and with no enemy before them. These accidents may be, and have been, looked upon as indicating imperfections in the ships or the manner in which they were handled; but it must be admitted that the ships are the best and best found in the world, and that they are commanded by the most skilful and highly trained seamen alive. And if peaceable ships fail in their manoeuvres when simply trying not to hurt each other, what will be the case of fighting ships when trying to do all they can to destroy each other? If the general impression as to the important part which the ram is to play in the naval combats of the future is ever realized, then certainty in manoeuvring must not only be of very great importance (this it has always been in sea fights), but it must occupy the very first place in the fighting qualities of the ship.

Now the results of the investigation of the effect of reversing the propellers on the action of the rudder appear to show that, however capricious the behaviour of ships has hitherto seemed, it is in reality subject to laws; and that by a series of careful trials the commander of a ship may inform himself how his ship will behave under all circumstances.

The experiments of the Committee on large ships have completely established the fact to which it was my principal object last year to direct attention, namely, that the reversing of the screw of a vessel with full way on very much diminishes her steering-power, and reverses what little it leaves; SO that where a collision is imminent, to reverse the screw and use the rudder as if the ship would answer to it in the usual manner is a certain way of bringing about the collision. And to judge from the accounts of collisions, this is precisely what is done in nine cases out of ten. In the paper of to-day I find the following (August 22, 1876):

"The Fatal Collision off Ailsa Craig.-The Board of Trade inquiry into the collision between the steamer Owl' and the schooner-yacht Madcap' was continued at Liverpool yesterday. Two passengers by the 'Owl' were recalled, and spoke to some of the facts of the collision. The night was not misty, though some rain had fallen. They saw the green light of the yacht shining brightly after the collision. William Maher, third officer of the Owl,' said it was the chief officer's watch at the time of the collision. ere were five able seamen in the watch. Witness and the chief officer

were on the bridge. One man was on the look-out from the starboard side of the bridge. His ordinary place was on the forecastle-head, but he was not placed there that night, as there was a heavy head sea, and the vessel was shipping water. His attention was called to a light by the look-out man. It was almost ahead about a mile and a half off. He could not at first distinguish whether it was red or green, as it was dim; but when he made it out to be a green light it bore two to three points on the port bow, and it was only three or four lengths off. He heard no order given to the man at the wheel when the light was first reported; but when witness found that it was a green light he ordered the helm hard aport. If the steamer had starboarded at this time she would have gone right over the yacht. The 'Owl' had been going at the rate of six or seven knots; but when she collided there was no way on her, the engines having been reversed. After the yacht went down the captain ordered a boat to be got out, but subsequently countermanded the order, on the ground that more lives would be lost, as it was not fit to go out. At the close of his examination the witness stated that he would not have gone out in a boat on such a night as that, even if the captain had ordered him-a remark which appeared to greatly astonish the nautical assessors."

He ported his helm to bring his ship round to starboard, but he also reversed his screw; and as he says nothing about having again starboarded his helm, it would appear that from the time of reversing the screw until the collision (time enough to stop the ship), she had moved straight forward or inclined to port. Had he not reversed his screw, but kept on full speed, it is clear the collision could not have happened, for at the time the collision did happen his ship would have been more than her own length away from the spot where the collision occurred. He admitted himself that to have starboarded his helm must have brought about the collision, so he ported his helm and reversed his screw, which, as it had the same effect, did bring about the collision.

Thus

From the Committee's report just read, it appears that a ship will turn faster, and for an angle of 30°, in less room when driving full speed ahead, than with her engines reversed, even if the rudder is rightly used. when an obstacle is too near to admit of stopping the ship, then, as was done in the case of the Ohio,' mentioned in my paper last year, the only chance is to keep the engines on full speed ahead, and so to give the rudder an opportunity of doing its work.

These general laws are of the greatest importance, but they apply in different degrees to different ships; and each commander should determine for himself how his ship will behave. A ship's ordinary steering-power may soon be learnt in general use, but not so the effect of stopping; there is thought to be a certain risk in suddenly reversing the engines, which any one in charge of a ship will shrink from, unless he knows it is recognized as part of his duty.

It is also highly important that the effect of the reversal of the screw should be generally recognized, particularly in the law courts; for in the present state of opinion on the subject, there can be no doubt that judgment would go against any commander who had steamed on ahead, knowing that by so doing he had the best chance of avoiding a collision, or who had ported his helm in order to bring his ship's head round to port, with the screw reversed. It seems to me, therefore, that it would be well if steps could be taken by this Association to bring the matter prominently before the Admiralty, the Board of Trade, and those concerned in navigation.

So far as the capabilities of each individual ship are concerned, there is no insuperable difficulty or risk about the experiments, and to have determined these will be a great point. When the officers know exactly what can be done in the way of turning their ships, and how to do it, the chances of accidents must be greatly reduced.

But at all events for fighting ships it is desirable that the officers should have experience beyond the mere turning powers of their own ships. When two ships are manoeuvring so as to avoid or bring about a collision, each commander has to take into account the movements of his opponent. To enable him to do this with readiness, it would be necessary to have friendly encounters. A fight between two ships whose captains had never before fought, would be like a tournament between two novice knights who had never practiced with pointless spears; and such a contest, although not unequal, must be decided by chance rather than skill.

Unfortunately sham fights or tournaments between ships with blunt rams would be about as dangerous as a real fight; and the chance of an accident would be far too great for such friendly tournament, however important, ever to become an essential part of the training of a naval officer, as they were of the knights of old. For although, should war arise, the danger from want of experience may be even greater than the danger of an accident in gaining such experience by friendly fights, yet, as the chance of war is always remote, the former risk would be preferred; and this is not all.

As yet there has been no such thing as a ramming fight between steamships; so that not only are our officers without actual experience, but even the rules by which they are instructed to act (the rules of naval tactics) are based entirely on theoretical considerations, and hence are very imperfect.

Now there appears to me to be a means by which experience of the counter-manoeuvring powers of ships, as well as the manoeuvring powers of single ships, could be ascertained without any of the risk and but little of the cost attending on the trials of large ships, and which, if not equal to an actual fight, would be very useful as a means of training the officers.

If small steam-launches were constructed similar to the ships, so that they represented these ships on a given scale (say one tenth linear measure), and their engines were so adjusted that they could only steam at what we may call the speed corresponding to that of the larger ships, then two launches would manoeuvre in an exactly similar manner to the large ships, turning in one tenth the room; and the time which the manœuvres with the launches would take would only be about half that occupied by similar manœuvres with full-sized ships. The only points in which it would be necessary that the model should represent the ship would be in its shape under water and as regards the longitudinal disposition of its weights. The centre of gravity should occupy the same position amidships, and the longitudinal radius of gyration of the model should bear the same proportion to that of the ship as the other linear dimensions. In other respects the model might be made as was most convenient. It might be made of wood, and so strengthened that two models might run into each other with impunity.

There would not be much difficulty in so strengthening the models, as the speed of the models would be very small. For instance, if the speed of the ship were 13 knots, then that of the model would be 4 knots.

The study of the qualities of ships from experiments on their models has not until recent years led to any important results. But this in great part was owing to the fact that proper account had not been taken of the effect of the wave caused by the ship and the consequent resistance. It was not

This shows approximately the effect of reversing the screw by the time the boats had lost all way.

E is the point at which the screws were reversed.

B position of Valetta after 25" when she had lost forward way.
A position in which the Valetta would have been after 25" had,
her screw not been reversed.

D position of the Barge after l' when she had lost all way. C position in which the Barge would have been after l' had the screw not been reversed.

E

This shows approximately the effect of reversing the screw by the time the boats had lost half their way.

E is the point at which the screws were reversed.

B position or the Valetta after 12" when she had lost half her forward way.

A position in which the Valetta would have been after 12" had her screw not been reversed.

D position of Barge after 30" when she had lost half her way. C position in which the Barge would have been after 30" had her screw not been reversed.