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[…] which things are given, may you have it, Gnomonic Reader, for demonstration, which in what follows Fineus, Clavius, Paduanus, and Betinus display, we all as others toward whom the Gnomists have recourse.
First, lay this sheet, which shows sundials, spread out upon a wooden table such that the depictions of everything appear properly, and so that they may be preserved for this task. Then place the pins where you mark the places for the nails in the cross, and let the pin themselves be of such a length outside as the distance implies, which runs perpendicularly from the same spots as the nails toward the equinoctial line, and it’s that line which, in all sundials given here, marks out the hours in due course by means of the diameter.
Place them in just this way, so that they are positioned at right angles, namely with such a ruler/frame that they are immovable, and erect, such that they do not seem to be leaning toward any particular side. When this is done perfectly, let it be observed in place, let it be placed with no structures blocking it on some wall which the rays of the sun strike from the south; on a wall without any slant; for this, just as for the meridian line, a slab is recommended, with a vertical guard, and certainly applied with a perpendicular ruler/frame, thus it may be stable, such that it cannot be moved by wind or some other unexpected occurrence. Do all this first.
In an Italian sundial, through ll parts of the year, there is information about the hours that occur daily, measuring the days from sunset, as it is experienced, and also data about celestial objects from month to month, through whose arcs the movements of the sun shine forth. However, in a Babylonian sundial, you will find the simple (simplices) hours measure from the rising of the sun; and note that where you discern imperial numbers placed along the meridian line, and beginning from the first hour to the tenth [inclusively] of the same sundial, you know that you are teaching in the whole year the increases or decreases of the days; thus the shadow of the stylus, or the sundial, which will lord over them by touching the diurnal arcs marked under the same numbers, will demonstrate that the shortest day in winter is eight hours, forty-two minutes; and the longest day in summer is fifteen hours and eighteen minutes, and thus the rest move with proportionate increase or decrease.
Indeed, the Planetarium—according to ancient rite and church calculations—measures all the days of the year in this world: whether they be shortest, or longest, the days are divided into twelve equal parts, and the shadow of the sundial successively shows from sunrise the first, second, third hour, etc.; and the sixth hour always marks midday.
And if you wish to determine with this sundial the quantity of equal hours from the sundial, you will be able to do this mathematically with the middle rulers, that is to say by considering how many minutes pass from sunrise to sunset during such a day, and how many hours during such a day must be assigned to the hours of the Planetarium, which divide the said day in question into twelve parts; likewise, how many Italian hours, for example, run, supposing the allotment of sixty minutes for each hour, from which it will be evident that the shadow of the Gnomon of the Planetary Clock regularly marks such an unequal hour, because it coincides with the rule for marking unequal hours, because it coincides, or with the hour fro the other three hands of the clocks remaining.
Note likewise that the cells are seven in number, which at the start, going from the right of the same Planetarium, have seven letters, namely D. L. M. M. G. V. S., steadfastly, day after day, or rather from hour to hour of any day. They specify the planet for a given day as well as any given hour. If, for example, you saim to know what planet the sun visits on Monday at one o’clock, you should know in advance that the seven aforementioned days (D. L. M. M. G. V. S.) indicate the first letters of the days of the week. Thus, D means “Dies Solis” (Sunday), L. “Dies Lunae” (Monday), M. “Dies Martis” (Tuesday), the other M. “Dies Mercurii” (Wednesday), G. “Dies Iovis” (Thursday, the I/J now being pronounced as a G in the Italian peninsula), V. “Dies Veneris” (Friday), and finally S. “Dies Saturni” (Saturday). Therefore, between the said cells, circle the letter L which designates Monday, and you will find the first hour of the said clock, which hour is called the first of those twelve parts into which the whole day is divided, whether those parts are of the same quantity of 60 minutes with hours of the other clocks equal (as happens in the vernal equinox and summer), or whether they are of a greater or lesser quantity of minutes at other times, as happens at other times of the year. Therefore, from the view of the first hour of the Planetarium, examine the signs through the aforementioned cell of the letter L and you will find the sun, on Monday at the first hour, rules the moon; and of the second hour, Saturn; and of the third hour, Jupiter, and so on.
Finally, the astronomicum—which the Spanish, French, Germans, and other such nations employ—uses twelve hours twice a day, by counting them from midnight to noon and then from noon to midnight. Now, because the sun does not suddenly rise over the horizon after midnight, and because it does not suddenly, once it has risen, illuminate southward-facing walls (or the southern side of anything), therefore the six hours after midnight are not included on this clock. [I.e., the sun can’t light up the calendar anyway]. Thus, with greatest ease, this diurnal division of hours will have escaped your method of pursuing knowledge at every moment, by which knowledge you may understand both the hours in Astronomica and the point during the day, in which astronomical clock as well besides twelve hours, you will see twelve other dotted, which were added expressly by my teacher’s studies, and so that you may point out the divisions of hours, and to complete the title of the Crucifixion, devised allegorically with adirable skill. Therefore, since these sundials will quickly open up for you all those pursuits of the Gnomists, which many are too tired to espouse at length, and the uses of all the nations of the world concerning the marking of hours for the elevation of our city, may they give this by way of epilogue: You, most learned Reader, should most earnestly express your gratitude for such a thing to P. Magnificus D. Virmundus Corius, an inventor second to none among Gnomonists. These things are for you, with respect to this page [?]. For one desiring an explanation for the illustrations and decorations with respect to these sundials, let Vega satisfy [?] in Lentide, whose index, in the phrase “Ring of Solomon,” will reveal all things, as thus prepared by my teacher, harmonizing in praiseworthy ways. Farewell.
