Posthuma Fosteri the description of a ruler, upon which is inscribed divers scales: and the uses thereof: invented and written by Mr. Samuel Foster, late professor of astronomie in Gresham-Colledg. By which the most usual propositions in astronomy, navigation, and dialling, are facily performed. Also, a further use of the said scales in deliniating of far declining dials; and of those that decline and recline, three severall wayes. With the deliniating of all horizontall dials, between 30 and 60 gr. of latitude, without drawing any lines but the houres themselves.

2. To finde the distance of the Sun from the Zenith.

The distance of the Sun from the Zenith is the arke Z S, therefore to finde the quantity thereof, you must first finde the pole of the circle NS Z, which is done after this manner.

Lay a Ruler from Z to T, and it will cut the cir∣cle in a, then take in your compasses a quadrant of the outward circle, and set it from a to b, then lay a ruler from Z to b, and it shall cut the Horizon in e, which point e is the pole of the circle ZTN.

Now to measure the arke Z S, you must lay a ru∣ler upon e and S; which will cut the outward circle in the point A, so shall A Z, being measured upon the line of Chords, give you the quantity of de∣grees contained in the arke Z S, which will be 40, equall to the complement of the Suns Altitude.

¶This latter proposition was inserted rather to shew how the arke of any great Circle of the Sphere (the sides of all Sphericall Triangles being such) may be measured, then for any need there was to finde the distance of the Sun from the Zenith, for that mighe have

been more easily effected, it being only the complement of the Suns Altitude; but ac∣cording to this operation, may the side of any Sphericall Triangle whatsoever be mea∣sured.

The line of Sines also will project the Analemma, as Master Gunter sheweth, if this proposition be added.

How to divide any line given, into such parts as the Scale of Sines is divided.

Which proposition may be done by that which is set down in the 1 Chapt. For if AD mn C were parts or divisions made equall to those upon the Scale of Sines, and CE were a line in the same manner to be divided: After you have prepared your work as is there prescribed, you need only to take the least distances between the points C nm D and the line AE, and insert the same into your given line, so shall the divisions thereof be proportionall to the line of Sines.