Range and Position Finders.

Evening Star, Issue 7412, 6 January 1888, Page 4

Range and Position Finders.

As our readers are aware, several of these instruments havt? been imported itito Australia, and have been or are being placed in position. They are, of course, used principally for coast batteries. 13y their help it is i possible for the officer directing the tiring to be a long distance from the guns, clear of the smoke and confusion, and in a position choson as giving the best possible \hw of the space swept by tire. The advantages gained by their use are at once apparent. It is a matter of indifference when they are used, whether Nos. 1 can seethe object they are firing at or not, and consequently guns can often be placed in more secure and sheltered positions than heretofore. Guns can be laid to fire over intervening high ground, which shuts out the view of the object from the gunners, as is actually done at present in Sydney Harbor, where the guns at Middle Head fire over South Head and command the approaches to Port Jackson from the south, the gunners making good although the targets cannot be seen fvom the battery, the guns being laid by quadrant, under telegraphic instruction from the signal station at South Head. The smoke Inseparable from heaVy firing, under these circumstances becomes rather useful than otherwise, as, if the wind is favorable, it screens the battery and prevents the enemy making accurate practice, while it in no way interferes with the officer in charge of the look-out station. Again, by arranging that the officer working the poaitionfiuder can himself fire the guns by electricity, he is in a position to fire either one or a whole group instantaneously. The general principle is as follows :—A carefully drawn map .of the water urea swept by the guns of the fort is prepared and divided by a number of segments of circles, which have the fort for their common centre. It is further marked by any number of right lines radiating from the fort, and it is consequently divided into a great number of practically email squares. This map is placed on a table in the position station, over which works an arm, having its pivot at the point representing the position of the fort. Resting on this arm is a telescope with which to watch the movements of the vessel to be fired upon. From the arm a pointer depends, so that it touches the map on the table, and is so adjusted that as the telescope is brought to bear on the ship, the arm works with it, and the pointer indicates on the map the particular portion of the water the vessel is travorsing. A scale gives the elevation, and all that is necessary for the observer to do is to telegraph to the fort the exact elevation and direction indicated, and on Woril Toeing received that these have been followed, the observer can fire the gun by electricity. Of course he has to anticipate the progress of the vessel, by giving his order so that when the gun or group of guns is fired they will be laid direct upon her.

This latter difficulty has lately been got ovei* by what is called " predicted firing." Major Watkin, in describing his invention before the Royal Artillery Association on a late occasion, said : "The latest pattern is a great improvement on the old positionfinder. We no longer use squares to signal to the guns very slightly in advance, but have resorted to what has been termed 'predicted firing.' We found that with recruits and men not expert with the training and elevating gear it was hopeless to follow a ship going at any speed, and that they required from half a minute to a minute to simply train and elevate. So now the position-limler traces the course of a ship, and when the guns are ready to lay predicts the position the ship will occupy half a minute or more in advance. The dials on the gun floor automatically indicate the range and training to hit that predicted position. When the guns arc laid an electric tube is inserted, and a signal goes up to the observing station that all is ready for firing. The non-eommis.sionedofficer in charge of the position-finder, which is of course laid on to the predicted position, looks through a telescope and watches for the appearance of the ships in the field of view ; and when she arrives at the cross-wire presses a button, and the guns are fired. Thus, if we have a small body of men well acquainted with the peculiarities of a fort and the working of a position-finder, the rest of the work could be efficiently done by militia or volunteers. At a recent practice at a moving target, towed in a zigzag course across the water, we succeeded in hitting the target five times out of ten rounds, the range varying from 2,000 to 4,000 yards, the gun being entirely laid by the predicted fixing method. One great advantage of position-finding is that the fort can really be commanded and fought by one officer." Speaking of night-firing, Major Watkin states: "An experiment was tried a short time ago, by the Royal Engineers, with the position-finder, for submarine mining, at Plymouth ; and it was found that with a very ordinary electric light we could follow a gunboat with care up to 2,oooyds. Now, it is just as easy to train a gun to a given number of degrees on the arc by night as by day ; and, therefore, with the aid of a position-finder, there would be no difficulty iu laying the guns at night." Major S. C. Pratt says : " I had the good fortune to witness an experiment on Major Watkin's system at Plymouth, under what we may call service conditions. Everything was tolerably unfavorable. The weather was bad ; the range was obstructed ; they had only recruits, who had been but a few days at drill, to serve the guns ; the guns were in casemates ; Major Watkin had only a very short time to put up his range-finder. Two 10-inch guns were fired by the recruits at a target going six miles an hour nearly two miles away, with a heavy sea in front of the range. The officer in the casemates had nothing to do except to look at a dial on the face of the wall, which gave him the training and elevation of the gun. Every now and then an electric signal came from a point above, at which the observer was, ' Are you ready '!' The gun was made ready and the men stood clear without any trouble about laying it. The observer from a distance, who has a clear range of vision, by putting his finger on an electric key sent off these two guns. You could see the shots in the air falling on the target at 3,ooojds range a few feet apart on the water-line."—From the ' Australian Naval and Military Gazette.'