idler gear, etc. Improper operation could also result in undesirable drops in boiler pressure and/or damage to the booster. Usage North America The booster saw most use in North America. Railway systems elsewhere often considered the expense and complexity unjustified. Even in the North American region, booster engines were applied to only a fraction of all locomotives built. Some railroads used boosters extensively while others did not. The New York Central was a fan of booster engines and applied them to all of its 4-6-4 Hudson locomotives. The rival Pennsylvania Railroad, however, used few booster-equipped locomotives. Canadian Pacific Railway rostered 3,257 steam locomotives acquired between 1881 and 1949, yet only 55 were equipped with boosters. 17 H1 class 4-6-4s, 2 K1 class 4-8-4s and all 36 Selkirk 2-10-4s. Australia In Australia, Victorian Railways equipped all but one of its X class 2-8-2 locomotives (built between 1929 and 1947) with a 'Franklin' two-cylinder booster engine, following a successful trial of the device on a smaller N class 2-8-2 in 1927. From 1929 onwards, South Australian Railways 500 class 4-8-2 heavy passenger locomotives were rebuilt into 4-8-4s with the addition of a booster truck . New Zealand NZR's Kb class of 1939 were built with a booster truck to enable the locomotives to handle the steeper grades of some South Island lines (particularly the Cass Bank of the Midland Line). Some boosters were later removed because of the gear jamming. Great Britain In Great Britain, eight locomotives of four different classes on the London and North Eastern Railway were equipped with booster units by Nigel Gresley. Four were existing locomotives rebuilt with boosters between 1923 and 1932: one of class C1 (in 1923); both of the conversions from class C7 to class C9 (in 1931); and one of class S1 (in 1932). The remaining four were all fitted to new locomotives: the two P1 2-8-2 locomotives, built in 1925; and two class S1 locomotives built in 1932. The boosters were removed between 1935 and 1938, apart from those on class S1 which were retained until 1943. An early type of booster used in Great Britain was the steam tender, which was tried in 1859 by Benjamin Connor of the Caledonian Railway on four 2-4-0 locomotives. Archibald Sturrock of the Great Northern Railway (GNR) patented a similar system on 6 May 1863 (patent no. 1135). It was used on fifty GNR 0-6-0 locomotives: