THE radiocarbon method has been used to test the hypothesis that the prominent rings found in certain calcite deposits of Moaning Cave in California represent annual growth variations. Carbon-14 an alyses were made on two samples taken, from a presumably active section of travertine covering a human femur (Fig. 1). When discovered in 1951, the specimen had 1,206 identifiable rings with an estimated 200 additional rings obscured1. Thus, if these rings formed annually and without interruption the bone at the centre became the nucleus of the cave formation about 1,400 years ago.