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 ...

OPERAT. III. To Compose the Globe, either by a Meridian Line, or without it, to the site of the World.

IF you have a Merid. line drawn, viz. a Line lying exactly North and South, place the Globe level with its Merid. directly over it, i. e. place so the little Notch in the Pedestal (markt S) that it cover the South∣ern extremity of the said line, and the Notch N the Northern, and then the Poles and Circles on the Globe will (without sensible error) corre∣spond with those in Heaven, and each painted Region or Countrey on it, will be turn'd towards the real one which it represents.

But if you have no line drawn, Know the day of the Moneth, and you have two quick waies to do this Operation without any forreign helps.

The Globe having in it smal pin-holes, on the several intersections of the Merid. with the aforesaid Diurnal Parallels, or (to be exacter) on each point of the Merid. which an imaginary Parallel of each fifth day would cut; for tho' we are to suppose Parallels for every day throughout

the year, yet there being no sensible difference in the Sun from 5 daies to 5 days, such holes will be abundantly sufficient; nay the aforesaid ones from ten Dayes to ten Days, may very well serve the turn in any ordinary Operation: I say, the Globe having holes in its Meridian at this distance, put the Zenith Pin, or, if you think better a Needle, in the Hole, which most agrees with the true day of the Month, and then exposing your Globe level to the Sun, do but move it till the shade of the said Needle or Pin falls directly along the Diurnal Parallel where 'tis placed; or, if it be not placed in any of the said Parallels, move the Globe till the shade falls parallel to the next Diurnal Parallel, and 'twill be as truly Compos'd as before, supposing you know (as we have already taught you) whether it be Forenoon or Afternoon when you operate; for, as in the Morning the Stiles of Dials cast their shades Westward, and in the Afternoon Eastward, so must your Needle or Pin do when the Globe is Compos'd.

But here the Reader must take notice, that in case the shade of the Needle or Pin will by no means fall sensibly parallel, but (as you move the Globe) draws nearer and nearer its being so, till at last it shortens to nothing, then the Sun is exactly South, and consequently your Globe is compos'd, as soon as the shade thus vanishes.

Now, Because the shadow of the Pin is on the Globe an Arch of a Great Circle, this way of Composing the Globe cannot be accounted Ma∣thematically true, For as the Sun approaches each Tropick and the Tro∣picks not Great Circles, it will happen Mornings and Evenings (when the Pin projects long shadows) that the shadow of the Pin will not ly exactly in the Parallel of the Day, but will (more or less) intersect it in the Center or Pin-hole. Therefore tho' the aforesaid way of Composing the Globe be true enough for ordinary uses, yet I shall give you two other waies without exception.

Observe the Concentrics between the North Pole and its Polar Circle, and first you will find that they are equal in number to the Parallels, ei∣ther from the Equator to the Tropick of Cancer, or to those from the said Aequator to Capricorn; for to avoid the confusion of too many Parallels, there are usually but 8 Northern and 8 Southern described on the Globe. 2ly. That they are distant from the Pole as the said Parallels are from the Equator. And 3ly. That they are markt not only with the Daies of the Month of the Northern Parallels, but with those of the Southern also. The Day of the Month then being (for example sake) Apr. 10. Move but the Globe (when level) till the shade of Extuberancy touches the Concen∣tric markt Apr. 10. and 'twill be truly Composed; supposing that the Eastern face of the Globe looks towards the Forenoon or Eastern parts

of Heaven, and the Western face towards the Afternoon. In like manner, If the Day of the Month or Suns Parallel be an imaginary one between any two that are exprest; for to avoid (as I mention'd) the confusion of too many Parallels there are usually but 8 Northern and 8 Southern de∣scribed; I say in like manner, If the Day of the Month, or Suns Parallel happens thus, let the said Shade but touch or fall proportionably between the correspondent Concentrics, and the Globe will be Compos'd, as before.

The reason of the Operation is this; The Sun illuminating (as has been said) half the Globe, the Shade of Extuberancy (or in other terms the Con∣fines between the Obscure and Illuminated parts) will be still 90 degrees from the point or place where the Sun is vertical; therefore if the Sun be (v. g.) in the Equator, the aforesaid Shade or Illumination must terminate in the Poles of the World; and when he is in the Parallel of Ap. 10. the Il∣lumination must fall short of the South Pole, and go beyond the North Pole as many degrees as the said Parallel declines from the Equator; But the Concentric of Ap. 10. is by Construction just distant from the Pole those degrees; Ergo when the said shade of Extuberancy or the Illuminati∣on touches this Concentric, the Globe must (if its Eastern face looks to∣wards the Fore-noon part of Heaven or the Western the Afternoon) be il∣luminated as the Earth is, and consequently Compos'd; for its correspond∣ing with the Earth in its site and position is all we mean by Composing.

As for the reason why I mark each Concentric with the 4 opposite Months, whereas the Parallels are markt only with 2 of them, 'tis that the Globe may be Composed by the help of the Northern Concentrics, even when the Sun is in his Southern Declension, it being more convenient and ready for one to cast his Ey on the North Pole than to stoop to the South Pole; about which otherwise there must have been the like number of Concentrics, and markt as the Southern Parallels are; I say this is the rea∣son of thus marking the Concentrics; for since the Sun in its Northern de∣clension illuminates beyond this Pole, he must in his Southern fall propor∣tionably short of it; therefore move the Globe as before (let it be Summer or Winter or any other time of the Year) till the said Illumination or Shade touch the Concentric markt with the day of the Month, and 'twill be still Composed.

The second way I shall defer to Operat. 10. because the intermediate ones conduce much to the facilitating it, as you'l see.

Notes

• Operat. 1. pag. 4.
• A way to Compose the Globe by the Sun.
• Operat. 2. pag. 7.
• A Memo∣randum.
• The first way of Com∣posing the Globe.
• The Demon∣stration.
• The 2d way vid. Op. 10.