before 18th July and current traffic was read for the first time.
(g) Later uses of the method
Refinements of the Indicator Method, whereby the second and fourth impulses
were given equal status with the others, and whereby a complete and systematic
determination of the wheel patterns was made possible, even when the PSI patterns
were initially unknown will not be described here.
It may be noted however that analysis by indicators still proved possible
and useful, even when the stereotyped beginnings were replaced by arbitrary
padding words as was the case from the middle of August onwards. However, after
July, Turing's method for analysing key from true depths was available, and
wheel patterns for September and October were actually broken on depths and near
depths. The indicator analysis was used only for the breaking of the indicator
At the end of July work on the Tunny cipher by the Research Section came to
an end, and was all taken over by a special "Tunny" Section. Later however the
Research Section made another contribution in the shape of the Statistical Method.