  An unexpected behavior of pure septic fields L = Q(D^1/7) with certain prime
radicands D congruent to 2 or 4 modulo 7, which split in the cyclotomic field
of seventh roots of unity, is proved by direct computation. Whereas the Galois
closures N = Q(zeta_7, D^1/7) of these fields contain relative differential
principal factorizations in the kernel of the norm of N/L, the class numbers of
L and N are not divisible by 7.
