About: http://webisa.webdatacommons.org/292628975

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	A port is cut in the piston head at its lowest point to allow liquid to flow past as the piston head moves with the gun; and the rate of this flow, especially during recoil, is controlled by the valve key.
http://www.w3.org/ns/prov#wasQuotedFrom	maritime.org