The English globe being a stabil and immobil one, performing what the ordinary globes do, and much more / invented and described by the Right Honorable, the Earl of Castlemaine ; and now publish't by Joseph Moxon ...

How to describe an Horizontal Dial by the Globe, for the Elevation of London.

The first way.

OPen your Compasses at 60 Degrees in any great Circle of your Globe, and draw on a sheet of Paper a blind Circle with a fair Diameter throu' it, for the Meridian or 12 a Clock hour line of your Dial; Then take with your Compasses in the Horizon of your said Globe, the several Distances between the next 8 morning or evening hour Circles and its Meridian or ordinary 12 a clock hour Circle, and marking these Distances successively in the blind Circle on both sides of its Diameter, they and the Center will be the Points by which you may draw all hour Lines from 4 in the Morning till 8 at Night; and if you would have a Dial bigger than the blind Circle, draw about it a bigger Circle, if a lesser a less: nay, if you describe any other Figure as an Oval, Square Oblong, &c. the said Points will as well guide your Ruler, as when the blind Circle it self was the Extremity or border of your Plane. But least this Direction should be too obscure for a Beginner, I will here adjoyn an Example.

Having opened your Compasses, as I said, at 60 Degrees in any great Circle of your Globe, and describ'd a blind Circle, to wit, I p T c, as in Scheme third, draw a fair line IT any how throu' the Center O for your Meridian or 12 a clock

hour Line; and by the way remember that in the Fabrique of this Dial you place the point I ever towards you, and T far∣thest from you, to the end you mistake not when directed to this or that hand. Having then proceeded thus far, put one foot of your Compasses on the Meridian or (according to the Polar Figures) the 12 a clock Circle of your Globe where it cuts the Horizon, and the other foot on the 1 a Clock Circle, and mark this distance in the blind Circle from I towards the left hand, to wit from I to k, and it will give you a point or mark for your 1 a Clock hour line, and from I to h towards your right hand the mark for your 11 a Clock hour Line. In the next place take in the said Horizon the distance between the 1 and 2 a Clock Circles, and place it from k onwards to l for a mark for your 2 a Clock Line, and from h to g for the 10 a Clock line, and so on till you come to r, 8 at night, and to a, 4 in the morning, which are the latest and earliest Summer hours. If then you would have a larger Dial de∣scribe a larger Circle, suppose, NESW; or if a lesser Di∣al, a lesser Circle, as MPQR, and laying your Ruler on the Center O, and on each of the former Marks or Letters in the said blind Circle successively, draw but a fair line to the de∣signed Limb or Border (whether it be a Circle; or the square VXYZ or any other Figure,) and your Dial wants nothing bdt a Cock; but remember that you need not draw your hour lines quite from the Center O, because meeting all there, they will be apt to blur; therefore describe about the said Center, at what distance you please, a little Circle (like γ ♌ λ) and your lines will terminate there with more neatness and convenience. Now if you have a mind to put on half hours and quarters, you will not much err if you divide each hour into four parts, but to be exact you must make use of your String, thus. You know that the distance between each hour-Circle in the Aequator is 15 Degrees, Draw therefore your String from the Pole throu' the Aequator of your Globe, over 7 degrees and 30 minutes, (or half the distance between each Hour Circle) and where the String cuts the Horizon there will be the true half Hour of that Hour; so that if you mark with your Compasses the said distance on the blind Circle, between the corresponding hour lines, the Ruler (pas∣sing

throu' that Mark and Center) will give you in the Bor∣der the place of that half hour; and in like manner you are to proceed in marking out the rest, as also the Quarters, and all other Subdivisions.

As for the Stile or Cock of this Dial, it must always at the Center make an Angle with the Meridian or 12 a Clock Line (OI) equal to the Distance between the Pole and the nearest part of the Horizon of the Globe; that is to say an Angle equal to the Elevation or Latitude of the Place; therefore your Dial being made (suppose) for London, open your Compasses at the aforesaid distance, or at 51 Degrees and ½, and placing one foot on I, the other will fall on K in the said blind Circle; so that drawing the blind line OK to π, you will have the Triangle IO π, which if you so erect, that the Point O lyes just on the Center, and the Base IO on your 12 a Clock line (or Substile) your Dial is finish'd.

And here you may take notice, that tho' this Stile be the Triangle IO π, yet you may fashion it into what shape you please, in case the side π O (which indicates or shows the Hour) makes still an Angle of 51 Degrees and 1 / 2 with the Meridian IO; nay, you may make it a Pin or upright Stile, as appears by the Perpendiculars AB, GH and π I, for ei∣ther of them will serve the turn by marking the hour with the shade of its Apex or Top: but then they must not be plac'd in the Center O, but thereon the Substilar, where (fal∣ling from the Indicating side O π) they stand Perpendicular to it; that is to say, the Pin AB (being part of the Trian∣gle or Stile IO π) must be erected at B, the Pin GH at H, and π I at I; and the reason, why they perform this Office, as well as the whole Triangle IO π is, because their Tops are parts of the Line O π, which is the only side of the said Triangle, that shows the Hour, as we mention'd before. Now for the De∣monstration of all, it follows in the next Operation.

Notes

• The Constru∣ction.
• An Example.
• How to draw the half hours, quarters, &c.