We have thus established the fact that one feature of the primitive Aryan accentuation, which consisted in the very natural process of placing the high accent on the first syllable of vocatives, was strictly preserved in Sanskrit, while in Greek and Latin it only left some scattered traces of its former existence. Without the light derived from Sanskrit, the changes in the accent of vocatives in Greek and Latin would be inexplicable, they would be, what they are in Greek grammar, mere anomalies; while, if placed by the side of Sanskrit, they are readily recognized as what they really are, remnants of a former age, preserved by frequent usage or by an agent whom we do not like to recognize, though we cannot altogether ignore him,—viz. chance.
Taking our position on the fact that change of accent in the vocative in Greek is due to the continued influence of an older system of Aryan accentuation, we now see how the change of nom. Ζεύς into voc. Ζεῦ, and of nom. Dyaús, into voc. Dyaû́s, rests on the same principle. In Sanskrit the change, though at first sight irregular, admits of explanation. What we call the circumflex in Sanskrit, is the combination of a rising and falling of the voice, or, as we should say in Greek, of an acute and grave accent. As Dyaús was originally Diaús, and is frequently used as two syllables in the Veda, the vocative would have been Díaùs, and this contracted would become Dyaus. Thus we have paribhvế from paribhûs. In Greek the facts are the same, but the explanation is more difficult. The general rule in Greek is that vocatives in ου, οι, and ευ, from oxytone or perispome nominatives, are perispome; as πλακοῦ, βοῦ, Λητοῖ, Πηλεῦ, βασιλεῦ, from πλακοῦς, οῦντος, placenta, βοῦς, Λητώ, Πηλεύς, βασιλεύς. The rationale of that rule has never been explained, as far as Greek is concerned. Under this rule the vocative of Ζεύς becomes Ζεῦ; but no Greek grammarian has attempted to explain the process by which Ζεύς becomes Ζεῦ, and nothing remains for the present but to admit that we have in it an ancient Aryan relic preserved in Greek long after the causes which had produced it had ceased to act. It would fall into the same category as εἶμι and ἴμεν. Here, too, the efficient cause of the length and shortness of the radical vowel i, viz., the change of accent, Sk. émi, but imás, has disappeared in Greek, while its effect has been preserved. But whatever explanation may hereafter be adopted, the simple fact which I had pointed out remains, the motive power which changed the nom. dyaús into the vocative dyaû́s, is the same which changed Ζεύς into Ζεῦ. Those who do not understand, or do not admit this, are bound to produce, from the resources of Greek itself, another motive power to account for the change of Ζεύς into Ζεῦ; but they must not imagine that a mere reference to a Greek elementary grammar suffices for explaining that process.
The passage in the Rig-Veda (VI. 51, 5) to which I referred is unique, and I therefore give it here, though it has in the meantime been most ably discussed by Benfey in his “Essay on the Vocative” (1872).
“Dyaû́ḥ pítaḥ pṛthivi mấtaḥ ádhruk
Ζεῦ πάτερ πλατεῖα μῆτερ ἀτρεκ(ές)
Ágne bhrấtaḥ vasavaḥ mṛláta naḥ[13]
Ignis φράτερ ϝέΣηϝες μέλδετε nos.”
This passage is clearly one of great antiquity, for it still recognizes Dyaús, the father, as the supreme god, Earth, the mother, by his side, and Agni, fire, as the brother, not of Heaven and Earth, but of man, because living with men on the hearth of their houses. Vasu, as a general name of the bright gods, like deva in other hymns, corresponds, I believe, to the Greek adjective ἐΰς. The genitive plural ἐάων is likewise derived from ἐΰς or vásus, by Benfey (l.c. p. 57), and dâtấ vásûnâm (Rv. VIII. 51, 5) comes certainly very near to δοτὴρ ἐάων. The only difficulty would be the ā instead of the η, as in ἐῆος, the gen. sing. of ἐΰς in Homer, a difficulty which might be removed by tracing the gen. plur. ἐάων back to a fem. ἐά, corresponding to a Sk. vasavî or vasavyâ. As to μέλδετε, it is phonetically the nearest approach to mṛlata, i.e., *mardata, though in Greek it means “make mild” rather than “be mild.” Mild and mollis come from the same root.
What gives to this passage its special value is, that in all other passages when dyaus occurs as a vocative and as bisyllabic, it appears simply with the udâtta, thus showing at how early a time even the Hindus forgot the meaning of the circumflex on dyaû́s, and its legitimate appearance in that place. Thus in Rv. VIII. 100, 12, we read,—
“Sákhe Vishṇo vitarám ví kramasva,