direction to the direction of the jet, whereas their motions along the jet are insignificant (see Table 2). Hence, we assume that the sources are caused by the interaction of the jet and clumps of ambient material as the jet sweeps across the clumps. In this model, the clumps will have apparent transverse velocities given by

$$v_T = r \beta = r \alpha v~, ~~~~~~~~~~~~~~~~~~~~~(8)$$

which, with the observed value of $\alpha$, becomes

$$v_T = 0.42 v (r/10")~. ~~~~~~~~~~~~~~~~~~~~~~~~~(9)$$

The proper motion measurements of all the sources are listed in Table 2. We believe that the apparent motions of source C could be due to the presence of an additional, time-variable component to the NW of the main component of source C (see Fig. 2). Source N-4 shows proper motions that are slightly below 4-$\sigma$ (see Table 2). However, these marginal proper motions are against the expected flow of the jet and, if real, are probably due to a “Christmas tree” effect more that to a real motion.

The velocity vectors of S-1 and N-1 are nearly transverse to the jet direction, and agree in direction with the sense of precession of the jet (see Fig. 8). These velocities are 