In a previous paper on “The Inner Structure of the Pearlite Grain” read to the Iron and Steel Institute in 1922 the author advanced views on the stereometry of the pearlite grain. It was shown that the angle of inclination of a secant plane ω could be computed from the equation cos ω = Δ 0 /Δ ω , (1) where Δ 0 is the actual distance between two consecutive cementite or ferrite lamellæ and Δ ω is the trace of that distance on the secant plane. It follows from (1) that Δ ω = Δ 0 sec ω. (2) As the diameter d c of a cementite lamella or the diameter d f of a ferrite lamella is a constant fraction of Δ, it may be assumed that d ω = d 0 sec ω, (3) where d ω is the trace of d 0 on the secant plane.