THE crater-lake of Kaalijärv, one of the group of craters on the Island of Oesel off the coast of Estonia, has been described on several occasions since 1827, and many suggestions have been made as to its mode of origin. In 1927 and 1929 Mr. I. Reinvald, Inspector of Mines in Estonia, made a detailed survey of the craters with borings and trenches, and he was himself convinced of their meteoritic origin, although he was then unable to find any traces of meteorites at the locality. With remarkable persistence he has again returned to the work of excavation, and in July last he was rewarded by finding in the smaller craters, Nos. 2 and 5, thirty small rusted fragments of nickel-iron, which on a polished and etched surface show a characteristic though rather unusual type of structure. These remnants of the Kaalijärv meteorite finally settle the question of the meteoritic origin of these craters.