While the semantron was inherited from Greece, the use of church bells was imported into Russia from Western Europe. The Russian word for bell is "kolokol", which comes from the German word "glocke", derived from the Latin "clocca", which in turn appears to come from the Irish "clog". The word for bell in Church Slavonic is "kampan", which is derived from Latin "campana". During the fifteenth century the semantron began to be gradually replaced by bells. At that time, several foundries for bell making were established in Russia. Russian church bells are commonly cast using a mixture of bronze and tin, often with silver added to the bell metal, to produce their unique sonority and resonance. Russian bells also tend to differ from Western bells in the proportion of their height to width, and the method of varying the thickness of the walls of the bell. The clapper ("tongue") of the bell also follows a different design than that used in the West.