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Frederick William Caswell Cock(s) (1863–1944) of the Day Gas Engine Co and the employee who actually designed the valveless two-stroke engine. Note: In his early life the surname is without the 's' but this is used in later records.
1863 Q4. Born at East Lambrook, Somerset, the son of Nathanial Cock, a brass and iron turner, and his wife Martha
1881 Frederick W. Cock living at 2 Alexandra Cottages, Weston, Somerset (age 17 born East Lambrook, Somerset), Engine Fitter. With parents Nathaniel (age 42 born Silton, Dorset), Brass and Iron Turner and his wife Martha (age 38 born Taunton). Also siblings John R. (age 14), Hannah W. (age 10), Herbert O. (age 6) and Benjamin S. (age 3). 
1891 Frederick W. C. Cocks living at 13 Chelsea Buildings, Bath (age 27 born West Lambrook, Somerset), Steam and Gas Engineer and Electrical Fitter. With wife Ada A. (age 25 born Cleave, Somerset) and son Frederick R. (age 3 born Bath). Also a boarder. 
1892 October 15th. Applied for a patent on an improvement to the two-port Day engine involving a third port (Patent number 18,513) and this was then assigned to Day.
1895 Listed as 'Cocks, Frederick W. C., engineer, 2 Lyndhurst Terrace', Bath 
1895-97 Moved from Bath to Erith, Kent to work for Easton and Anderson who had licenced the engine
1901 Frederick W. C. Cocks living at 5 Ladywell Park, Lewisham (age 39 born East Lambrook, Somerset), General Engineer viz. Steam, Gas, Hydraulic, Electric. With wife Ada A. (age 35 born Cleeve, Somerset) and children Frederick R. (age 13 born Bath), Leonard C. (age 9 born Bath), Victor H. (age 7 born Bath) and Gladys I. A. (age 4 born Erith, Kent). 
1944 Q2. Died in Dartford district. (Listed as Frederic W. C. Cock)
A Day-Cock engine is in the London Science Museum and has a bore of 51mm and a stroke of 83mm.
A 2-hp Day-Cock engine is in the Deutsches Museum in Munich and has a bore of 82mm, a stroke of 133mm and a capacity of 0.86 litres.