Horometry

Horometry is a mathematical art that demonstrates how, at any appointed time, the precise customary reckoning of time may be known for any given place. These words are smooth, plain, easy English, but their meaning reaches farther than you would readily imagine. Some part of this art was called in old times Gnomonice, and more recently Horologiographia, and in English it may be called dialing. The use is ancient, and the invention is older still. The use plainly appears to have been in existence, at least, more than two thousand three hundred years ago:

(4. Reg. 20.)

In King Achaz's dial, then, by the sun, showing the distinction of time. By sun, moon, and stars this dialing may be carried out, and the precise time of day or night known. But the demonstrative drawing of dials of every sort requires good skill in astronomy and in elemental, spherical, phenomenal, and conic geometry. Then, to apply the grounds of the art to any regular surface offered in any place, and there to describe, in every manner of way, how the usual hours may truly be determined by the sun's shadow, will be found no slight work for a draftsman: so to draw and prescribe the sun's motion to the breadth of a hair. In this feat (in my youth) I invented a way how, in any horizontal, mural, or equinoctial dial, etc., at all hours (the sun shining) the ascending sign and degree may be known. Which is a thing very necessary for the rising of those fixed stars whose operation in the air is plainly of great power. I say no more of its use here. But since human affairs require knowledge of times and moments when neither sun, moon, nor star can be seen, mechanical industry first invented how, by water running in orderly course, the time and hours might be known, of which the famous Ctesibius was the inventor, a man whom Vitruvius justly extolled to the sky. After that, hours were measured by running sand; then by Trochilike driven by weight; and in recent times by Trochilike driven by a spring, without weight. All of these, directed by sun or stars at certain times, require oversight and correction according to the heavenly equinoctial motion, besides the inequality of their own working. There remains (without any parabolic meaning here) among the philosophers,

(A perpetual motion.)

a more excellent, more useful, and more marvelous way than all these: to have the motion of the Primouant (the first equinoctial motion) imitated by nature and art, which you shall hereafter understand more of through further search in weightier studies. And so it is time to finish this account of the division of time used in our common and private affairs, the benefit of which no man would want who knows how to spend his time.

Horometrie is a mathematical art. It shows how, at any appointed time, the exact customary reckoning of time can be known for any given place. These words are smooth, plain, easy English, but their meaning reaches further than you would readily imagine. Some part of this art was called Gnomonice in old times, and more recently Horologiographia, and in English it can be called dialing. The use is ancient, and the invention is older still. The use seems to have been in place at least more than two thousand three hundred years ago:

(4. Reg. 20.)

in King Achaz's dial, then, showing by the sun the divisions of time. This dialing can be done by sun, moon, and stars, and the exact time of day or night known. But drawing these dials demonstratively, of all kinds, requires good skill both in astronomy and in elemental, spherical, phenomenal, and conic geometry. Then, to use the foundations of the art on any regular surface that comes to hand in any place, and on it (in any possible fitting position) to set out every way in which the usual hours can be truly determined by the sun's shadow, will be found to be no easy painter's work. That means painting and setting out the sun's motion to the width of a hair. In this feat (in my youth) I invented a way: in any horizontal, mural, or equinoctial dial, etc., at all hours (when the sun shines), the sign and degree ascending can be known. This is very necessary for the rising of those fixed stars whose influence in the air is plainly very great. I will say no more about its use. But since people's affairs require knowing times and moments when neither sun, moon, nor star can be seen, mechanical skill first invented how the time and hours could be known by water running at a steady rate. The famous Ctesibius was the inventor of this, a man whom Vitruvius rightly praised to the skies. After that, hours were measured by running sand. Then by Trochilike with a weight, and more recently by Trochilike with a spring, without a weight. All of these need oversight and correction by the direction of the sun or the stars (at set times), according to the heavenly equinoctial motion, besides the unevenness of their own working. There remains among the philosophers (not speaking figuratively here),

(A perpetual motion.)

a way more excellent, more useful, and more marvelous than all these: to have the motion of the Primouant (or the first equinoctial motion) imitated by nature and art. You will understand more of this later, through further search in weightier studies. And so it is time to finish this discussion of the divisions of time used in our public and private affairs. No man who knows how to spend his time would want to be without its benefit.