A Bipolar, Knotty Outflow with Velocities of 500 Kilometers per Second or above from the Engraved Hourglass Planetary Nebula MyCn 18

High spectral resolution observations of the [N II] 6548 + 6584 Å and Hα emission lines from the young planetary nebula MyCn 18 have been obtained using the Manchester echelle spectrometer combined with the Anglo-Australian Telescope. These spatially resolved spectra reveal not only the kinematical characteristics of the two bright rings of emission, which define the well-known ``engraved hourglass'' structure of this object, but also the dramatic motions of the faint, irregular knots of emission observed outside the main nebular structure. The knots are moving with velocities >=500 km s^-1 away from the central star, an order of magnitude faster than the motions observed from the main nebula, making them among the highest velocity outflows ever observed from a planetary nebula. A bipolar, rotating, episodic jet mechanism is favored for their origin.