  The semileptonic decays $\bar{B}\to D(D^*)\pi\ell\bar{\nu}$ are analyzed by
heavy quark and chiral symmetries. The branching ratio is of order of a few
percent for $\dpi$, but it is much smaller for $\dstar$, of order
$10^{-4}-10^{-5}$. The decay mode $B^-\to D^+\pi^-e^-\bar{\nu}_e$ provides a
nice place for extracting the $D^*D\pi$ coupling constant from the semileptonic
decays of a $\bar{B}$ meson. Two types of weak radiative decays of $\bar{B}$
mesons and bottom baryons are studied. The decay $\Lambda_b^0\to
\Lambda^0\gamma$ receives the electromagnetic penguin $b\to s\gamma$
contribution and has a branching ratio of order $2\times 10^{-5}$. The
radiative decays $\bar{B}\to D^*\gamma,~
\Lambda_b^0\to\Sigma_c^0\gamma,~\Xi_b^0\to \Xi_c^0\gamma$ and
$\Xi_b^0\to{\Xi'}_c^0\gamma$ occur through $W$ exchange accompanied with a
photon emission and their branching ratios are estimated to be much smaller. We
conclude that the weak radiative decays of bottom hadrons are dominated by the
short-distance electromagnetic penguin mechanism.
