Chandas (Original Sanskrit Text)

Principles
The main principle of Vedic meter is measurement by the number of syllables. The metrical unit of verse is the pada ("foot"), generally of eight, eleven, or twelve syllables; these are termed gāyatrī, triṣṭubh and jagatī respectively, after meters of the same name. A ṛc is a stanza of typically three or four padas, with a range of two to seven found in the corpus of Vedic poetry. Stanzas may mix padas of different lengths, and strophes of two or three stanzas (respectively, pragātha and tṛca) are common.

Syllables in a pada are also classified as metrically short (laghu "light") or long (guru "heavy"): a syllable is metrically short only if it contains a short vowel and is not followed by consecutive consonants in the same pada. All other syllables are long, by quality (having a long vowel or diphthong) or by position (being followed by a consonant cluster.) Comparison with the Avestan literature shows that originally there were no constraints on permissible patterns of long and short syllables, the principle being purely quantitative. Vedic prosody innovated a number of distinctive rhythms:

* The last four syllables of a pada, termed the cadence by Indologists, are usually iambic or trochaic. This is mainly a strict alternation in the penultimate and antepenultimate syllables, as the final syllable can be of either weight.
* A caesura is found after the fourth or fifth syllable in triṣṭubh and jagatī padas, dividing the pada into an opening and break before the cadence.
* The break very often starts with two short syllables.
* The opening shows an iambic or trochaic tendency in keeping with the cadence, though the first syllable can be of either weight, the alternation being in the second and third.

There is, however, considerable freedom in relation to the strict metrical canons of Classical Sanskrit prosody, which Arnold (1905) holds to the credit of the Vedic bards:
“ It must be plain that as works of mechanical art the metres of the Rigveda stand high above those of modern Europe in variety of motive and in flexibility of form. They seem indeed to bear the same relation to them as the rich harmonies of classical music bear to the simple melodies of the peasant. And in proportion as modern students come to appreciate the skill displayed by the Vedic poets, they will be glad to abandon the easy but untenable theory that the variety of form employed by them is due to chance, or the purely personal bias of individuals; and to recognize instead that we find all the signs of a genuine historical development. ”
 

Classification
Arnold (1905) uses the term dimeter for metrical schemes based on the 8-syllable (gāyatrī) pada, there being a two-fold division of a pada into opening and cadence; and the term trimeter for schemes based on 11-syllable (triṣṭubh) or 12-syllable (jagatī) padas, the division being into opening, break and cadence.

The principal difference between the two forms of trimeter is in the rhythm of the cadence: generally trochaic for triṣṭubh padas and iambic for jagatī padas. Except for one significant collection, gāyatrī padas are also generally iambic in the cadence. The compatibility of iambic cadence underlies the significant variety of mixed meters combining gāyatrī and jagatī padas.
[edit] Dimeter forms

Metres with two to six gāyatrī padas are named dvipadā gāyatrī, gāyatrī, anuṣṭubh, pańkti and mahāpańkti. Of these, only the gāyatrī and anuṣṭubh are frequently found.

Traditional literature
While Chandas (छंदः), the study of Vedic meter, is one of the six Vedanga ("limb of the vedas"), no treatises dealing exclusively with Vedic meter have survived. The oldest work preserved is the Chandas-shastra, at the transition from Vedic to Classical (Epic) Sanskrit poetry. Later sources are the Agni Purana, based on the Chandas shastra, chapter 15 of the Bharatiya Natyashastra, and chapter 104 of the Brihat-samhita. These works all date to roughly the Early Middle Ages. Vrittaratnakara of Kedarabhatta, dating to ca. the 14th century, is widely known, but does not discuss Vedic meter. The Suvrittatilaka of Kshemendra was also influential, and valuable for its quotations of earlier authors.

A well-known quantitative scheme in the traditional literature classifies the common meters according to the syllable count of a stanza, as multiples of 4: thus, dvipadā virāj (20), gāyatrī (24), uṣṇih (28), anuṣṭubh (32), bṛhatī (36), pańkti (40), triṣṭubh (44), and jagatī (48). This scheme omits the original virāj entirely (with 33 syllables) and fails to account for structural variations within the same total syllable count, such as the 28 syllables of the kākubh (8+12+8) versus the uṣṇih (8+8+12), or the 40 of the later virāj (4x10) versus the pańkti (5x8). More comprehensive schemes in the traditional literature have been mainly terminological, each distinct type of stanza carrying its own name. The classification is exhaustive rather than analytic: every variant actually found in the received text has been named without regard to any need for metrical restoration.