Summary: A military training film demonstrating the principles of elevation laying incorporating ratio of movement and range finding in a 6 inch CP gun.
Description: (Reel 1) Film begins with "jolly" music and a telescopic, masked picture of a woman in a bathing suit drying herself. A serious voiceover indicates that although this is interesting it is not what laying is all about! There are four cases of laying but the two most common types are the rocking bar and autosight. Pointer arrows indicate their position on a CU of the 6 inch CP II gun. There follows a breakdown of the parts and their roles. The rocking bar layer keeps the pointer of the bow water line on target/stern water line if the target is moving away. The autosight is explained on a demonstration model with the cover stripped away. Diagram of purpose of autosight ie meeting of line of sight and trajectory of shell. This trajectory relies on the quadrant elevation ie the elevation of the gun and the angle of sight represented diagrammatically. A change in the angle of sight and quadrant elevation is the ratio of movement which is measured by the autosight. However in practice, the state of the tide (datum) must be added to the calculation and both the trajectory and angle of sight must be altered by the same amount to remain on target. The tide lever performs this function, operating the cam but not the barrel. (Reel 2) More distant objects require a rangefinder director to target them. This is found in the battery observation point (BOP) and is operated by three men. The No 1 looks through the telescope ie range finds; the No 2 reads the range scale and the No 3 transfers this information to the transmitting dial which in turn is passed to the receiving dial on the gun. The battery commander decides whether the autosight or rangefinder should be used. The film concludes with the simulation of an action; lots of explosions, CU of gun at work and shooting of two simulated targets as well as the tow rope pulling them along.
