Next a depth of July 21st with indicators K O W P A E N G F Q B Z was
successfully attacked. All the wheel patterns of this depth, with the exception
of these of the two "motor" wheels ( with periods 37 and 61) were the same as in
W A O S H but these two patterns were different.
From these depths the following conclusions could be drawn:
(i) The order of the wheels was fixed.
(ii) The PSI patterns remained unchanged over periods which
could exceed one month.
(iii) The X patterns remain unchanged over periods of
(iv) The patterns of the motor wheels were changed
It could now be assumed that one reason why the attempts to set messages not
in depth had failed was that the wrong motor wheel patterns had been assumed. The
attempts were now resumed, but no assumptions were made about the motor patterns.
Messages intermediate in time between K O W P A E N G F Q B Z and W A O S H were
taken, so that there could be no serious doubt about the pattern of the X and