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 p929  Polus

Article by Philip Smith, B.A., of the University of London
on pp929‑930 of

William Smith, D.C.L., LL.D.:
A Dictionary of Greek and Roman Antiquities, John Murray, London, 1875.

POLUS (πόλος), in astronomy, is a very difficult word to explain in a perfectly satisfactory manner, on account of the various senses in which it is used. In such a case, the only safe guide to the original meaning of a word is to determine, if possible, its sense in the earliest passage in which it occurs, and to compare that sense with what is known of the etymology of the word. Now it is evident that πόλος contains the root ΠΕΛ, which we find in πέλομαι and other words, and the fundamental idea attached to which appears to be that of motion. Then, turning to the Greek authors, we find the word first occurring in the well-known passage in which Aeschylus (Prom. 427) speaks of Atlas as supporting on his shoulders the pole of heaven, that is, the vault of the sky, which was called πόλος in accordance with the notion, which prevailed from the time of Thales, that the sky was a hollow sphere, which moved continually round the earth, carrying the heavenly bodies with it (comp. Eurip. Or. 1685; Pseudo-Plat. Axioch.  p930 p371B; Aristoph. Av. 179; Alex. ap. Ath. p60A; Ukert, Geog. d. Griech. u. Röm. vol. I pt. II p115; Grote, History of Greece, vol. II pp154, 155). The next passage, in order of time, is that in which Herodotus (II.109) says that the Greeks learnt from the Babylonians πόλον καὶ γνώμονα καὶ τὰ δυωκαίδεκα μέρεασον τῆς ἡμέρης, where the later commentators and lexicographers for the most part explain the word as meaning an astronomical instrument, different from the γνώμων or sun dial. Mr. Grote (l.c.) interprets the passage as signifying that the Greeks "acquired from the Babylonians the conception of the pole, or of the heavens as a complete hollow sphere, revolving round and enclosing the earth." But Herodotus certainly seems to be speaking of something more definite and specific than a mere conception respecting the sky; and, on the whole, the most probable explanation is that of Scaliger and Salmasius, as modified by recent astronomers and scholars (see Bailly, Delambre, Letronne, and Creuzer, as quoted by Bähr, ad loc.), namely, that the word signifies the concave hemispherical sun-dial, made in imitation of the heavenly sphere, and hence called by the same name, πόλος, which was the earliest form of the sun-dial, inasmuch as it required less skill than the delineation of a sun-dial on a plane surface. The γνώμων was not another different sort of sun-dial, but the index, or, as we still say, gnomon of the dial itself, the shadow of which, falling upon the meridian lines of the sun-dial, indicated the hours of the day as marked by the motion of the sun in the true heavenly πόλος; so that, in fact, the words πόλον καὶ γνώμονα together describe the instrument. Pollux (IX.46) explains πόλος as meaning ὡρολόγιον, in a passage which he quotes from the Gerytades of Aristophanes; and Lucian (Lexiph. 4) speaks of the γνώμων overshadowing the middle of the πόλος, — a striking confirmation of the explanation we have given. The γνώμων alone was, in fact, not originally a sun-dial, but a mere upright stile, the length of the shadow of which was measured, to obtain a rough notion of the altitude of the sun and thence of the time of the day: afterwards, a dial was added with lines marked upon it, so as to form a true sun-dial, which was still called γνώμων. The simple gnomon was used by the Greek geographers to determine the latitude of places. (Comp. Horologium.)1

For the other meanings of πόλος, see the Greek Lexicons.

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The Editor's Note:

1 In the article Horologium will be found statements differing in some minor points from those in this article: such differences are unavoidable when a difficult subject is discussed by different writers; and they may even be useful to the reader who wishes to examine the question thoroughly. [Ed.]

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