The Charana-vyuha, or "Exposition of Schools," a supplementary work of the Sutra period, mentions as the five çakhas or "branches" of the Rigveda, the Çakalas, the Vashkalas, the Açvalayanas, the Çankhayanas, and the Mandukeyas. The third and fourth of these schools, however, do not represent different recensions of the text, the sole distinction between them and the Çakalas having been that the Açvalayanas recognised as canonical the group of the eleven Valakhilya or supplementary hymns, and the Çankhayanas admitted the same group, diminished only by a few verses. Hence the tradition of the Puranas, or later legendary works, mentions only the three schools of Çakalas, Vashkalas, and Mandukas. If the latter ever possessed a recension of an independent character, all traces of it were lost at an early period in ancient India, for no information of any kind about it has been preserved. Thus only the two schools of the Çakalas and the Vashkalas come into consideration. The subsidiary Vedic writings contain sufficient evidence to show that the text of the Vashkalas differed from that of the Çakalas only in admitting eight additional hymns, and in assigning another position to a group of the first book. But in these respects it compares unfavourably with the extant text. Thus it is evident that the Çakalas not only possessed the best tradition of the text of the Rigveda, but handed down the only recension, in the true sense, which, as far as we can tell, ever existed. The text of the Rigveda, like that of the other Samhitas, as well as of two of the Brahmanas (the Çatapatha and the Taittiriya, together with its Aranyaka), has come down to us in an accented form. The peculiarly sacred character of the text rendered the accent very important for correct and efficacious recitation. Analogously the accent was marked by the Greeks in learned and model editions only. The nature of the Vedic accent was musical, depending on the pitch of the voice, like that of the ancient Greeks. This remained the character of the Sanskrit accent till later than the time of Panini. But just as the old Greek musical accent, after the beginning of our era, was transformed into a stress accent, so by the seventh century A.D. (and probably long before) the Sanskrit accent had undergone a similar change. While, however, in modern Greek the stress accent has remained, owing to the high pitch of the old acute, on the same syllable as bore the musical accent in the ancient language, the modern pronunciation of Sanskrit has no connection with the Vedic accent, but is dependent on the quantity of the last two or three syllables, much the same as in Latin. Thus the penultimate, if long, is accented, e.g. Kalidasa, or the antepenultimate, if long and followed by a short syllable, e.g. brahmana or Himalaya ("abode of snow"). This change of accent in Sanskrit was brought about by the influence of Prakrit, in which, as there is evidence to show, the stress accent is very old,