One of the most far-reaching and important events of this reign was the invention of the _yi-du_, or set of terminations used in the margin of Chinese texts to aid the reader in Koreanizing the syntax of the Chinese sentence. We must bear in mind that in those days reading was as rare an accomplishment in Sil-la as it was in England in the days of Chaucer. All writing was done by the _a-jun_, who was the exact counterpart of the “clerk” of the Middle Ages. The difficulty of construing the Chinese sentence and using the right suffixes was so great that Sŭl-ch‘ong, the son of the king’s favorite monk, Wŭn-hyo, attempted a solution of the difficulty. Making a list of the endings in common use in the vernacular of Sil-la he found Chinese characters to correspond with the sounds of these endings. The correspondence was of two kinds; either the _name_ of the Chinese character was the same as the Sil-la ending or the Sil-la _meaning_ of the character was the same as the ending. To illustrate this let us take the case of the ending _sal-ji_, as in _ha-sal-ji_, which has since been shortened to _ha-ji_. Now, in a Chinese text nothing but the root idea of the word _ha_ will be given and the reader must supply the _sal-ji_ which is the ending. If then some arbitrary signs could be made to represent these endings and could be put in the margin it would simplify the reading of Chinese in no small degree. It was done in this way: There is a Chinese character which the Koreans call _păk_, Chinese _pa_, meaning “white.” One of the Sil-la definitions of this character _sal-wi-ta_. It was the first syllable of this word that was used to represent the first syllable of the ending _sal-ji_. Notice that it was not the name of the character that was used but the Sil-la equivalent. For the last syllable of the ending _sal-ji_, however, the Chinese character _ji_ is used without reference to its Sil-la equivalent. We find then in the _yi-du_ as handed down from father to son by the _a-jun’s_ of Korea a means for discovering the connection between the Korean vernacular of to-day with that of the Sil-la people. It was indeed a clumsy method, but the genius of Sŭl-ch‘ong lay in his discovery of the need of such a system and of the possibility of making one. It was a literary event of the greatest significance. It was the first outcry against the absurd primitiveness of the Chinese ideography, a plea for common sense. It was the first of three great protests which Korea has made against the use of the Chinese character. The other two will be examined as they come up. This set of endings which Sŭl-ch‘ong invented became stereotyped and through all the changes which the vernacular has passed the _yi-du_ remains to-day what it was twelve hundred years ago. Its quaint sounds are to the Korean precisely what the stereotyped clerkly terms of England are to us, as illustrated in such legal terms as _to wit_, _escheat_ and the like. There is an important corollary to this fact.