  Neutron scattering experiments have been performed on
Sr$_{14}$Cu$_{24}$O$_{41}$ which consists of both chains and ladders of copper
ions. We observed that the magnetic excitations from the CuO$_2$ chain have two
branches and that both branches are weakly dispersive along the $a$ and $c$
axes. The $\omega$-$Q$ dispersion relation as well as the intensities can be
reasonably described by a random phase approximation with intradimer coupling
between next-nearest-neighbor copper spins $J$=11 meV, interdimer coupling
along the c axis $J_c$=0.75 meV, and interdimer coupling along the a axis
$J_a$=0.75 meV. The dimer configuration indicates a quasi-two-dimensional hole
ordering, resulting in an ordering of magnetic Cu$^{2+}$ with spin-1/2 and
nonmagnetic Cu, which forms the Zhang-Rice singlet. We have also studied the
effect of Ca substitution for Sr on the dimer and the hole ordering.
