CORNISH LANGUAGE. This extinct language belonged to the Brythonic group of the Celtic division of the Indo-Euro pean family of languages. It is, therefore, akin to Welsh and to Breton—indeed it is suggested that up to i400–i600 a Cornishman could understand a Breton speaker. It is, however, a characteris tic feature of Cornish, even in old forms, to change non-initial t and d into s or z. With the Reformation, it decayed as the Prayer Book and the Scriptures circulated in English—so that the people became bilingual, and then lost their original speech, though there is evidence that people who lived into the i9th century were able to converse in it. The modern speech of western Cornwall still contains Celtic words and "since by Pol, Tre and Pen, you may know the Cornish men," from Tamar to Land's End are found personal and place names of Celtic origin.