  Superconductivity in FeSe was investigated under high pressure through the
measurements of DC magnetization by using a diamond anvil cell. We successfully
observed that the disappearance of the superconductivity as a results of the
appearance of the non-superconducting ortho I\hspace{-1pt}I phase above $\sim$7
GPa ($\sim$5 GPa), when Ar (glycerin) is used as the pressure transmitting
media. Contrary to this, it has been found that the superconductivity even
survives under pressure above 7 GPa, when the thickness ($t$) of a
platelet-single crystal specimen is reduced. The survival of the
superconductivity above 7 GPa is consistent with a previous observation under
hydrostatic pressure by using a cubic anvil apparatus, suggesting that the
hydrostaticity of the pressure is improved by reducing $t$. It is also inferred
that the appearance of the ortho I\hspace{-1pt}I phase is due to uniaxial
stress along the [001] direction.
