though the surviving evidence has mostly to do with the birlinn in a naval context, there is independent evidence of mercantile activity for which such shipping would have been essential. there is some evidence for mercantile centres in islay, gigha, kintyre and knapdale, and in the fourteenth century there was constant trade between the isles, ireland and england under the patronage of local lords. otherwise the chief uses of the birlinn would have been troop-carrying, fishing and cattle transport.