=>It does not stick to the glass surface.
=>The vapors of mercury have no pressure.
=>It can be easily found in the natural state.
=>It is opaque so can be seen easily through the glass.

Mercury is a metal and the density is higher than any other liquid at normal temperature. Being brighter it can be seen inside the tube and can be read against a scale. Mercury has a very low vapor pressure, so it is more sensitive to the changes in the atmospheric pressure and rises more quickly to record the changes in the atmospheric pressure.Similarly freezing point is much lower than other fluid so it can record the atmospheric pressure at temperatures below that of 0 degrees centigrade.