THE ROYAL ARTILLERY INSTITUTION. 
373 
strain; but, for other reasons to be mentioned further on, no more dish 
should be given than necessary for the safety of the spokes. The 
amount of dish in a wheel is measured along its axis, from the point A 
(Fig. 2), where the prolongation of the face of the spoke meets that 
Fig. 2. 
axis, to the point B, where the perpendicular let fall from the extremity 
of the face at the bosom of the felloe meets the same axis. This in the 
O.P. field wheel of 5 ft. diameter is 3*375 ins. (measured close above 
the nave instead of along the axis it amounts to 2\ ins., and hence 
is usually, though incorrectly, said to be \ in. to 1 ft.) In the N.P. 
field wheel, the dish has been reduced to 2 ins., and experiment 
has shown that it cannot be further reduced with safety to the 
spokes, except in some cases, where the dish of a low front wheel is 
made to suit the track of the hind wheel. The amount of dish in 
wheels not of 5 ft. diameter is proportional to that in the 5 ft. wheel 
(that is, to 3*375 ins. if O.P., and to 2 ins. if N.P.), for the relative 
lengths from the axis to the bosom of the felloe. 
Dishing a wheel carries with it some minor advantages—for in¬ 
stance, giving greater width between the wheels above the axletree 
