  The results of investigations of the dissociation of a $^{14}$N nucleus of
momentum 2.86~A~GeV/c in photo-emulsion are presented. The main characteristics
of these reactions, that is the cross sections for various fragmentation
channels, are given.
  The fragmentation was analyzed by means of an invariant approach. The
momentum and correlation characteristics of $\alpha$ particles for the
$^{14}$N$\to3\alpha$+X channel in the laboratory system and the rest systems of
3$\alpha$ particles were considered.
  The results obtained for the $^{14}$N nucleus are compared with similar data
for the $^{12}$C and $^{16}$O nuclei.
