• The cold water cistern is fixed at a high level .
• Raise the gauge to a height at which the sharp edge of the notch is exactly level with the top of the valve connection.
• The surface of the liquid is flush with the floor of the tunnel.
• Oxygen could have been maintained at a level of about 0.02% of the total composition of the atmosphere.
• For electrons in the same principal level ...
• On the molecular level , diffusion is the result of ...