CARLSBAD CAVERNS NATIONAL PARK, a tract of about 720 ac. in south-east New Mexico, U.S.A., set apart in 1923 as a Government reservation. The series of caverns from which it is named was formed by the dissolvent action of water on original beds of rock salt, limestone and gypsum in the predom inating shale. Its total extent is not known, but is probably much greater than that of the present area of the reservation. One of the most notable discoveries is the Big Room, a cavern over 2 m. in length with a maximum width of 400 ft. and 348 ft. in height, containing a great variety of stalactites and stalagmites and por tions of white limestone and onyx marble.