The cold salt water is pumped through the extensive cast-iron radiators of the different cold rooms and the temperature regulators automatically open or shut the valve at the inflow of the cold salt water.
For many years it has been demonstrated, notably in the great Berlin aquarium, that marine animals and plants may be transported a long distance from their native habitats and then live on in aquaria with unimpaired health and growth. Hence it became an essential part of the plan to include marine organisms within the field of work of the institution and a complete equipment was installed for the investigation of problems of marine biology. Natural sea water, from the zoological
| A | B |
| Fig. 14. A. Carbonic-acid Cooling Machine with condenser, pumps for the compression of carbonic acid gas and for the circulation of the cooled salt water. | |
| B. One of the Cold Rooms with the cast-iron radiators for the circulation of the cold salt water. | |
station in Triest, is brought in car loads of thirty casks, each containing 500 liters. It is not difficult to maintain the proper concentration of salts and the same water can be used for years. It is not more expensive than artificial sea water, which is apt to vary in its constitution. Non-corrosive substances like glass, porcelain, glazed clay, cement, wood, hard rubber and lead lined with tin, were used in the construction of the aquaria for sea water. A plan of these aquaria, with the associated apparatus for aeration (Fig. 15), shows the distribution of sea water from the elevated reservoir (A), to cement basins (D), or to the smaller isolation jars in the next compartment. The effluent water, after being cleansed by running through the filter (H), is stored in the subterranean cistern (K), and thence driven by the
