  We present the first set of detailed molecular line maps of the region
associated with the giant Herbig-Haro flow HH 300, from the young star IRAS
04239+2436. Our results indicate that the red lobe of the HH 300 flow is
depositing a fair amount of momentum and kinetic energy over a notable volume
of its host dark cloud. This makes HH 300 a key player in the evolution and
fate of its parent cloud. The redshifted molecular outflow lobe of HH 300 is
1.1 pc long and 0.3 pc wide, and has a very clumpy structure. The density,
velocity, and momentum distributions in the outflow indicate that the observed
clumps arise from the prompt entrainment of ambient gas. Bow shock-shaped
structures are associated with the clumps, and we hypothesize that the shocks
are produced by different mass ejection episodes. Lines drawn from IRAS
04239+2436 to each of these clumps have different orientations on the plane of
the sky, and we conclude that HH 300 is a precessing and episodic outflow. The
observations include a map of the red lobe in the 12CO(2-1) line, with a beam
size of 27'', and more extended maps of the outflow region in the 12CO(1-0) and
13CO(1-0) lines, with 45'' and 47'' beam sizes, respectively. We obtain a steep
power-law mass spectrum for HH 300, which we believe is best explained by the
evolution of the outflow mass kinematics. In addition, our 13CO observations
show that the HH 300 flow has been able to redistribute (in space and velocity)
considerable amounts of its surrounding medium-density gas.
