​KODAIKANAL, a sanatorium of southern India, in the Madura district of Madras, situated in the Palni hills, about 7000 ft. above sea-level; pop. (1901), 1912, but the number in the hot season would be much larger. It is difficult of access, being 44 m. from a railway station, and the last 11 m. are impracticable for wheeled vehicles. It contains a government observatory, the appliances of which are specially adapted for the study of terrestrial magnetism, seismology and solar physics.