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Training in Fire Control: the "Dotter"

Catalogue number

Admiral Sir Percy Scott and naval gunnery

As the performance of naval guns improved so the distance for engagement increased and the control of gun fire became more and more important. One of the pioneers of naval gunnery and director firing was Admiral Sir Percy Scott (1853 – 1924) of the Royal Navy. Scott devised and developed numerous systems to improve gunnery and increase the number of hits despite Admiralty hesitation and obstruction. One device that turns up in old photographs is the dotter, a training machine for gunlayers by which the gun team can develop their skill in coordinating the union between following the target in the eye sight and laying the gun. Basically, the dotter is a carrying frame within which a target can be moved up and down as well as sideways. Fixed to the gun barrel is a pointer that is also held in the frame. The target is to the back of the frame and the pointer to the front. When the gun crew consider that the gun barrel/pointer is on target, “fire” the gun. By an electro-magnetic system, the pointer moves to hit and mark the target with a dot (hence the name “dotter”).

The Naval Annual, 1913, Griffin & Co.


Catalogue number

Admiral Sir Percy Scott and naval gunnery

In this side view of the dotter, we can see the link between the gun barrel and the pointer fixed to the carrying screen. Operators move the target horizontally and vertically using hand wheels whilst the gun crew use elevation and traversing of the gun to move the pointer in the frame. When the two coincide, the gun trigger is pulled and the pointer marks the target.

The Naval Annual, 1913, Griffin & Co.


Catalogue number 40257

A French design Dotter

The quarter deck has been cleared and the dotter moved out of the way but we can see all the principle parts of the training device. Following publication of the initial dotter design, other variants were made. Here the controls are on the right-hand part of the frame The thin wire coming back from the gun barrel may be to connect the gun trigger to the pointer.

13.6cm x 9.6cm Gelatin silver print


Catalogue number 66035

Details of the French dotter

Here the electro-magnet of the pointer is fixed to the barrel but displaced to one side. The target with the paper to be marked is in place and the officer is noting down the score. This dotter is on the French battleship Iéna prior to 1907.

Recto: "Fire control school" in French

8.8cm x 13.8cm Printed image


Catalogue number 73032

Another version of the dotter system, Justice, 1909

This photograph shows blacksmiths at work on the French battleship Justice. To the right of the group is a dotter seen from the rear and showing the holder for the pointer on the gun barrel. There is also a black square of unknown function fixed to the right of the target. Two such black squares are visable in catalogue number 40257 above.

23cm x 15.8cm Printed image


Catalogue number 73033

Fire control training on the battleship Justice, 1909

This dotter system is mounted in front of the forward 12-inch turret of the battleship Justice. We can see the pointer mechanism fixed inboard on the starboard gun barrel. The hand wheels for lateral and horizontal movements are on the starboard part of the frame and a counter-weight maintains the wires taut.

23cm x 15.8cm Printed image

Catalogue number 112111

Dotter frame on a French destroyer

Dotter systems were found on all sizes of vessels and here is one on a French destroyer. The rails on which the target slides appear to be curved to take into account the arc described by the gun when elevating. The operating wheels can be seen to the right. There is another graduated frame of unknown origin up by the bridge.

Verso: Postcard franked "1918"

14cm x 9cm Printed image