Some comparative data of the "King" class and other loco-
motives referred to is given below, iliumrating the continuous
growth in power of G.W.R. engines.

GREAT WESTERN RAILWAY PASSENGER LOCOMOTIVE
            DEVELOPMENT.

                                1837          1851         1909          1923            1927
                                North         Lord of      North*        Caerphilly      King
                                Star.         the Isles.   Star.         Castle.         George V
                                                                             V.
CYLINDERS:                      (2)           (2)          (4)           (4)             (4)
Diam. and Stroke -             16x16        18x24        14.1/4x26       16x26      16.1/4x28
DRIVING WHEEL:
Diameter                       7ft. 0 in.    8ft. 0 in.   6ft. 8Ģin.    6ft. 8Ģin.      6ft. 6in
BOILER PRESSURE:
Lbs. per sq. in.               50            140          225           225             250
HEATING SURFACE:
Total--Sat. and Sup.sq. ft.   694.7         1,750        2,014.4       2,312           2,514
GRATE AREA:Sq. ft.            13.62         24.0         27.07         30.28           34.3
TRACTIVE EFFORT: 
 m.e.p.=85% B.P.              2,070         9,640        25,085        31,625          40,300
WEIGHT OF
ENGINE: Tons                  18.5          41.9         75.6          79.84           89
RATIO:
Lbs. Tractive Effort,
per ton                      111.9         230          321.7         396             452.8

                        *Since converted to" Castle " class.