126 CHALLENGER 



The zinc is coated with an emulsion said to contain egg-yolk 

 and is a pleasing pale yellow in colour. The light makes the 

 emulsion exposed to it soluble in water while those parts covered 

 by the design remain insoluble. The soluble parts can then be 

 removed by washing and by a series of processes the plate can 

 be made to take bitumen where the image is required and the 

 plate is ready for use as a printing plate. The zinc plates are 

 manufactured in suitable sizes for reproducing charts and are made 

 with a distinct grain in their surface which retains moisture. This 

 in turn repels greasy substances such as printer's inks ; thus if the 

 plate is moistened, ink rolled over it will adhere only to the 

 bitumen-coated image. A piece of chart paper placed in pressure 

 contact with the printing zinc can then be made to accept the 

 image. The old proving press in Challenger did just this; the plate 

 and the paper were placed face to face on the flat bed and by 

 turning a handle a pressure roller w^as made to move across the 

 press to transfer the image. The plate had to be inked up by 

 hand after each copy of a chart was printed. There was little 

 mechanical and nothing swift about the method. 



The most suitable persons to operate this equipment were 

 members of the civil staff at the Hydrographic Supplies Estab- 

 lishment at Taunton. Volunteers from this branch of the 

 Hydrographic Department were not lacking and a lithographic 

 draughtsman, a printer and a photographer had been selected for 

 this duty in the ship. But what naval rank or rating should these 

 men hold? Authority had searched for a precedent and found one 

 at last in the Royal Marines who had, for some long forgotten 

 purpose, employed a printer in their ranks. So the men from 

 Taunton must become Marines, but time was short and they could 

 only be spared for one day to make this startling transition. 



Sergeant Crowford, tall and with a fighter pilot's moustache, 

 was the draughtsman, cheery Cockney Laws was the printer, and 

 Corporal Lyons the photographer. They felt more like over- 

 harnessed and overladen beasts of burden when at last they 

 reached the ship lying at her berth in Sheerness Dockyard. In 

 their unfamiliar uniforms, webbing equipment and heavy field- 

 boots they stumbled under their loads of kit. For were they not 

 going overseas? The Royal Marines must be ready for anything 

 from ceremonial parades to commando attacks in any climate 



