Messrs. Belliss and Co. of Birmingham exhibited one of three air compressors to be installed in H.M.S. Royal Oak; designed to produce high-pressure air for charging and firing torpedoes, they were capable of compressing 80 cubic feet of air to a pressure of 1,700 pounds per square inch. The compressor exhibited at the Royal Naval Exhibition had been tested by running it for three hours against a full load of 1,800 pounds per square inch, and it had supplied 10 cubic feet of air at a pressure of 1,800 pounds per square inch in 19 minutes.