My reason for offering the present contribution to a subject no longer considered as affording opportunities for remarkable discoveries is the following: Among the characteristic terms employed by students of Old French philology there are two which, consecrated by long usage, occur more frequently, probably, than any others. These two are “free “(frei, libre) and “checked” (gedeckt, entravé); they are used to refer to the position of vowels in Popular Latin, the vowel being called “free” when standing before a single consonant or certain consonant combinations, “checked” in other circumstances. Now I dare say that there is no definition of such fundamental importance which betrays more inconsistencies and difficulties to the careful scholar than does this one as stated in its present form in the various manuals on Old French. After seeking in vain either to find any single definition that seemed satisfactory or to combine the statements of different scholars into one comprehensive presentation of the point in question, I concluded that there must be something radically wrong with the traditional method of expressing the definition, and determined to make an independent investigation of the whole matter.