DIALING, the art of drawing dials, on any given plane, or on the surface of any given body. See DIAL.
The Greeks and Latins called this art gnomonica and scithetica, by reason it distinguishes the hours by the shadow of a gnomon. Some call it photo-scithetica, by
Plate XCII.
Bull. Sculp.
Dialing. by reason the hours are sometimes shewn by the light of the sun. Lastly, others call it horologio-graphy.
The antiquity of dials is beyond doubt. Some attribute their invention to Anaximenes Milefius; and others to Thales. Vitruvius mentions one made by the ancient Chaldee historian Berofus, on a reclining plane, almost parallel to the equinoctial. Aristarchus Samius invented the hemispherical dial. And there were some spherical ones, with a needle for a gnomon. The discus of Aristarchus was an horizontal dial, with its limb raised up all around, to prevent the shadows stretching too far.
But it was late ere the Romans became acquainted with dials. The first sun-dial at Rome was set up by Papirius Curfor, about the year of the city 460; before which time, says Pliny, there is no mention of any account of time but by the sun's rising and setting: it was set up at or near the temple of Quirinus, but went ill. About 30 years after, M. Valerius Messalla being consul, brought out of Sicily another dial, which he set up on a pillar near the rostrum; but for want of its being made for that latitude, it could not go true. They made use of it 99 years; till Martius Philippus set up another more exact.
But there seem to have been dials among the Jews much earlier than any of these. Witness the dial of Ahaz; who began to reign 400 years before Alexander, and within 12 years of the building of Rome; mentioned by Isaiah, chap. xxxviii. verse 8.
The first professed writer on dialing is Clavius; who demonstrates all, both the theory and the operations, after the rigid manner of the ancient mathematicians; but so intricately, that few, we dare say, ever read them all. Dechales and Ozanam give much easier demonstrations in their Courses, and Wolfius in his Elements. M. Picard has given a new method of making large dials, by calculating the hour-lines; and Mr de la Hire, in his Dialing, printed in 1683, a geometrical method of drawing hour-lines from certain points determined by observation. Eberhardus Welperus, in 1625, published his Dialing, wherein he lays down a method of drawing the primary dials on a very easy foundation. The same foundation is described at length by Sebastian Münster, in his Rudimenta Mathematica, published in 1551. Sturmius, in 1672, published a new edition of Welperus's Dialing, with the addition of a whole second part, about inclining and declining dials, &c. In 1708, the same work, with Sturmius's additions, was republished with the addition of a fourth part, containing Picard's and de la Hire's methods of drawing large dials. Paterfon, Michael, and Muller, have each wrote on dialing, in the German tongue; Coetius in his Horologio-graphia Plana, printed in 1689; Gauppenius, in his Gnomonica Mechanica; Bion, in his Use of Mathematical Instruments; and the late ingenious Mr Ferguson, in his Select Lectures. See the article DIAL.