Unique swimming pool illumination furnished by underwater floodlights

A unique electrical installation, consisting of an underwater illumination system, has recently been placed in operation in a large bathing pool in the vicinity of San Diego, California. Embedded in the walls of this pool is a set of large flood lights, placed at a depth of 9 feet. The lighting units are enclosed in a large pyramid-shaped casting, having a vent at the top leading through a goose-neck to a manhole back of the pool walls. The lamp unit is protected from the water by an 18-inch disk of Pyrex glass 7/16 inches thick. Difficulties as to the cracking of heavy plate glass had been numerous until the adoption of the heat-resisting glass. Water on one side of the glass at low temperature and the heat generated by a 500-watt lamp in the unit on the other side of the glass, together with moisture, condensation, and other mechanical factors, have. provided considerable basis for experimentation on this installation.