  Here we report a comprehensive study of the crystal structure, resistivity,
and alternating-current magnetic susceptibility in single crystals of
La$_3$Ni$_2$O$_7$, with a hydrostatic pressure up to 104 GPa. X-ray diffraction
measurements reveal a bilayer orthorhombic structure (space group $Amam$) at
ambient pressure and a transformation into a tetragonal phase (space group
$I4/mmm$) at ad critical pressure of $\sim$14 GPa. The transport measurements
reveal a right-triangle shape superconducting region with a maximum $T_c$ of 83
K at 18.0 GPa. The superconductivity is gradually suppressed when applying a
higher pressure, but it can persist up to 90 GPa. Importantly, we measured the
Meissner effect of superconductivity using an alternating-current magnetic
susceptibility technique under pressure and estimated the maximum
superconducting volume fraction of being 48$\%$ at 19.4 GPa. Thus, we
demonstrate the bulk nature of superconductivity in the bilayer nickelate
La$_3$Ni$_2$O$_7$ under high pressure. The intimate connection among the
superconductivity, the oxygen content, and the tetragonal structure are
discussed.
