  A method in which electromagnetic properties of hadrons are studied by direct
simulation of dynamical photon effects is applied to the extraction of the
isomultiplet structure of the octet baryons. Using 187 configurations at
$\beta=5.7$ with Wilson action, and up and down quark masses determined from
the meson spectrum, the nucleon splitting is found to be $1.55(\pm 0.56\; \rm
stat)$ MeV; the hyperon splittings are found to be
$\Sigma^{0}-\Sigma^{+}=2.47\pm 0.39$, $\Sigma^{-}-\Sigma^{0}=4.63\pm 0.36$,
$\Xi^{-}-\Xi^{0}=5.68\pm 0.24$ MeV. Estimated systematic corrections arising
from finite volume and the quenched approximation are included in these
results.
