  We realize a novel high flux source of cold atoms and molecules employing
hydrodynamic enhancement of an effusive aperture at cryogenic temperatures.
Molecular oxygen from the source is coupled to a magnetic guide, delivering a
cold, continuous, guided flux of 3e12 oxygen molecules per second, with a
molecule temperature of a few kelvin. The dynamics of the source are studied by
creating and spectroscopically analyzing high-flux beams of atomic ytterbium.
