The attenuation length of the gamma -families with SigmaE(gamma) greater th
an or equal to 100 TeV (N-fam = 1003), lambda (att) = (77 +/- 3) g/cm(2) an
d their vertical intensity I-vert = 0.63 +/- 0.04 m(-2 .) year(-1) . sr(-1)
are determined front the angular distribution. The experimental data are c
ompared with model simulations.