The relation between flame height, L, width of burning zone, Dw and rate of burning per unit are, m of wood cribs for a range of experimental conditions is of the form L/Dw = A(m/(??(gDw)))^2/3 where g is the acceleration due to gravity and ? is a density taken as a constant for a particular fuel. Although the value of A depends on the shape of the burning zone and the species of wood, it is sufficiently accurate for most purposes to assume its value is 40 when ? is taken nominally as the density of air equal to 1.3*10^-3 g/cm3.