• 1
    Water from tanks and reservoirs at the Societ.y's Aquarium has bee11 examined over a period of a year with respect to excess base, hydrogen ion concentration salinity, oxygen content, and pal tial pressure of carbon dioxide.
  • 2
    Similar estimations have been carried ont on fresh sea-water sent froin tile Bay of Biscay, Plymouth outside sea-water, Plymouth dquariuin water, aud tank water from University College Aquarium, London.
  • 3
    In all cases the values are found to deviate from the normal to a greater or less extent.
  • 4
    Plymouth Aquarium water maintains a nearly constant pH, as it is treated with lime, but is supersaturated with carbon dioxide.
  • 5
    The Society's Aquarium shows the greatest variation in hydrogen ion concentration and partial pressure of carbon dioxide, but the animals adapt themselves to this.
  • 6
    The rate at which the excess base alters in the Aquarium when a new consignment of water is used was examined.
  • 7
    The advantages of liming aquarium water are discussed.