Device for displaying the time by means of the shadow of a gnomon or style thrown by the rays of the sun on a graduated disk. It is generally agreed that by the "steps of Ahaz" (II Kings xxi. 9, 10; Isa. xxxviii. 8, Hebr.) some device for measuring time, in the form of a sun-clock, is intended. The expression was so understood by some of the old versions (Targ. Sym. ὡρολóγιον Vulg. "horologium"); but there are no means of determining with certainty the nature, shape, and construction of the contrivance. The view that a dial in the stricter sense of the term—that is, a plane with a graduated scale and a vertical style or gnomon—is meant, is not supported by the text, since the usual and natural meaning of is "steps," not "degrees."
Following the literal and usual meaning of the words, most exegetes assume that the מ were actual steps; that is, a circular staircase leading up to a column or obelisk, the shadow of which, falling on a greater or smaller number of the steps, according as the sun was low or high, indicated the position of the sun, and thus the time of day. Such an obelisk was erected during the reign of Augustus, on the Campus Martius in Rome. As, according to the account in II Kings, the shadow could go forward or recede ten steps, the step-clock of Ahaz must have had at least twenty steps, each of which, therefore, did not mark a full hour of the day, but some smaller period of time. Herodotus (ii. 109) ascribes to the Babylonians the invention of the pole (i.e., the concave dial) and the gnomon, and the division of the day into twelve parts. As Ahaz had intercourse with the Assyrians (compare II Kings xvi. 10), it is likely that he obtained from them a Babylonian model for his clock.
In 'Eduy. iii. 8 the stone-clock and its style (properly "nail") are mentioned (). Maimonides, in his commentary, describes it as a circle on a broad, smooth stone set into the ground, and marked with straight lines, which bore the numbers of the hours. The style, the height of which was usually less than one-fourth the diameter of the disk, cast a shadow upon the lines and indicated the number of hours passed.
- Geret, De Sole Tempore Hiskiæ Retrogrado, 1673;
- Sahm, De Regressu Solis Tempore Hiskiæ, 1689-96;
- Martini, Von den Sonnenuhren der Alten, Leipsic, 1777;
- Von Gumpach, Zeitrechnung der Babylonier, p. 25, Heidelberg, 1852;
- J. W. Bosanquet, in Transactions of the Society for Biblical Archæology, 1874, iii. 33;
- S. Beswick, The Shadow on the Dial of Ahaz, in Biblia, 1896, viii. 309;
- Müller, Bibel und Gnomik. Eine Apologetische Studie über die Sonnenuhr des Königs Ahas, in Natur und Offenbarung, 1902, xlviii. 5-7.