the earliest reference to the Backus engines appears ot be form the American Machinist of January 15, 1891. Backus engines were protected from infringment by several patents. the earliest of record was ascribed to Sylcanus D. Sheppard in 1894, with another following in 1896. As the engines were improved, new patents were secured, including one by J.F. Denison in 1901. The horizontal engines were available in sizes form 1 to 75 horsepower, and continued to use hot tube ignition even though some companies were devisng various electric ignition systems. The improved horizontal engines were of four-cycle design.