The discovery of a large number of beat Cepheids in the Large Magellanic
Cloud in the MACHO survey, provides an opportunity to compare the
characteristics of such Cepheids over a range of metallicities. We produced a
large grid of linear nonadiabatic pulsation models using the OPAL opacity
tables and with compositions corresponding to those of the Milky Way, and the
Large and Small Magellanic Clouds. Using the relationship between the period
ratio and the main pulsation period, we are able to define a range of models
which correspond to the observed beat Cepheids, and thereby constrain the
physical characteristics of the LMC beat Cepheids. We are also able to make
some predictions about the nature of the yet-to-be-discovered SMC beat
Cepheids.Comment: 20 pages, 6 embedded Postscript figures, uses aasms4.sty. Accepted
for publication in the 1997 September A