Lieutenant Commander Halsey Powell, Commander, Parker, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters
U.S.S. P A R K E R
5 August, 1917.
From: Commanding Officer(Lieut-Commander Halsey Powell).
To : Commander, U.S. Naval Forces Operating in European Waters.
Subject: Methods used.
1. Due to the fact that it will be necessary when opening fire on a submarine, to fire within a couple of seconds after she had been sighted, the following scheme is used on board this ship.
At night all guns are set at 0 with scale deflection at 50. First shot to be fired at night will be point blank. This is used when the night is dark and is not used at twilight, dawn in strong moonlight, or when object can be seen 1500 to 2000 Yards.
2. In the daytime, or when object can be seen 1500 to 2000 yards a different scheme is used, which is as follows:
Bearing degrees and deflection scales are marked on the guns’ recoil circle, which is painted on the deck. The scales are worked out for speed at 20 knots, this being the speed at which the ship immediately goes when submarine is sighted. The bearing of the target is given to the guns in degrees from the bridge and the gun captain coaches the pointers on by looking at the bearing under the breach of the gun and at the same time picks off the deflection scale corresponding to the bearing at a speed of 20 knots, which is also right under the breach of the gun. The sight setter also gets this as he crosses the deck and sets the deflection. The range is constantly kept, and is not changed at any time at 2000 yards. As a consequence the first shot is gotten off with unknown range or scale. This gives a shot near enough to spot, and has the advantage of starting the ba[l]l.
The talkers on the bridge and the spotters also have a scale similar to the one at the gun, consequently when they take charge they know what range and deflection was used for the first shot. From this point the talkers put the range and scale on the clocks and the spotters take charge.
Bearing indicators are instruments similar in principle to peloruses. They have been fitted to fore and main tops and will be fitted to all lookout stations. These instruments, roughly made, give the bearing to within one or two degrees (see sketch[).] We find lookouts have no trouble in giving the bearing from 0 to 360 degrees by means of this instrument, and since this is a system always used in our Navy, it is not thought desirable to change to British system.
Two so-called range clocks are mounted on the bridge to aid the talkers in keeping track of scale and range. These clocks are placed near the pelorus stands so that at night, after firing the guns, light can be turned on the pelorus stand and will shine on the clock, allowing the talkers to keep track of the range and scale. In addition each talker procures a hand flash light (dimmed) at general quarters, which he will be able to shine on clock in case the electric circuit fails. The torches are kept in a rack in the chart house and are not allowed to be taken out except at general quarters (see scetch). Of course it will be much better, if possible, to have clock with radium hands and numbers so that face can be seen without resorting to flashlights, or for that matter radium hands should be fitted on all clocks, torpedo stands, torpedo directors, compasses, range lights and sights and wherever possible to fit them.