  We report the discovery of 20 1H/2H and 7 F/1H beat Cepheids in the SMC by
the MACHO Project. We utilize the 20 1H/2H stars to determine lightcurve shape
for the SMC second-overtone (2H) mode of Cepheid pulsation. We predict, similar
to the findings of Alcock et al. (1997, ApJ, submitted), that 2H Cepheids will
have nearly or purely sinusoidal light variations; that the P-L relation for 2H
Cepheids will not be distinguishable from the P-L relation for 1H Cepheids
within photometric accuracy; and that 2H stars may be discernable from F and 1H
stars using the amplitude-period diagram and Fourier parameter progressions for
periods P < 0.7 days, our current sample 2H period limit.
