  Observations of stellar prominences on young rapidly rotating stars provide
unique probes of their magnetic fields out to many stellar radii. We compare
two independently obtained datasets of the K3 dwarf Speedy Mic using the
Anglo-Australian Telescope (AAT) and the ESO Very Large Telescope (VLT). Taken
more than a fortnight apart they provide the first insight into the evolution
of the prominence system on such a young rapidly rotating star. The largest
prominences observed transiting the stellar disc are found at very similar
rotational phases between the epochs. This suggests that the magnetic
structures supporting the prominences retain their identity on a two to three
week timescale. We identify prominences as transient absorption features in all
lines of the Hydrogen Balmer series down to H_10. We use the ratios of the
prominence EWs in these lines to determine their column densities in the first
excited state of hydrogen. We determine the optical depths, finding prominences
to be rather optically thick (\tau \approx 20) in the H_alpha line. The total
hydrogen column density and thus the prominence masses are determined via
observations of the CaII H&K lines. We find typical masses for four of the
largest prominences to be in the range 0.5 - 2.3 x10^{14} kg, slightly larger
than giant solar prominence masses. Rotationally modulated emission is seen
outside of the H_alpha line. These loops of emission are shown to be caused by
prominences seen off the stellar disc. We find that all of the large emission
loops can be associated with prominences we see transiting the stellar disc.
This combined with the fact that many prominences appear to eclipse the
off-disc emission of others, strongly suggests that the prominence system is
highly flattened and likely confined to low stellar latitudes.
