“…While tables for the least-squares fitting of Markoff serial variation functions in the neighbourhood of the origin, though being computed, are not yet available, it is usually sufficient to calculate serial variation statistics for lags of, say, I, 2, 3, 4, 5, 10, 15, 25 and perhaps 50, to plot the logarithm of the variograms, and to try various curves of the family (cf Jowett (1955» log Os = log (I -p8) + const.…”