Larger and smaller semantra have been used, the smaller being sounded first, followed by the larger, then by those of iron. Theodore Balsamon, in a treatise on the subject, compares the sounding of the little, great and iron semantra to the preaching of the Law and of the Gospel, and the Last Trumpet. He also says that the congregations were summoned by three semantra in monasteries, and only by one large one in parish churches. Moreover, he emphasises the persistence of the semantron in the East as a symbolic manifestation of difference with the Latin West (it remains unclear if some isolated practices in the West such as the Basque "txalaparta" are associated with the pre-schism liturgy); in Byzantium, the use of bells did not really gather momentum until after the Fourth Crusade, and at the Fall of Constantinople semantra still outnumbered bells by a five-to-one ratio. Semantra, from their size and shape, furnished formidable weapons, and were sometimes so used with fatal effect in a church brawl. One reason why semantra continue to be used in southeastern Europe in particular is that the ringing of bells was outlawed during Ottoman times under Islamic rule, forcing monasteries to use the semantron instead; the practice then became customary, though in Bulgaria it largely fell into disuse after independence.