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.

About this Item

Title: 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.
Author: Foster, Samuel, d. 1652.
Publication: London :: printed by Robert & William Leybourn, for Nicholas Bourn, at the South entrance into the Royall Exchange,; 1654.
Rights/Permissions: To the extent possible under law, the Text Creation Partnership has waived all copyright and related or neighboring rights to this keyboarded and encoded edition of the work described above, according to the terms of the CC0 1.0 Public Domain Dedication (http://creativecommons.org/publicdomain/zero/1.0/). This waiver does not extend to any page images or other supplementary files associated with this work, which may be protected by copyright or other license restrictions. Please go to http://www.textcreationpartnership.org/ for more information.
Subject terms: Astronomy -- Early works to 1800.; Nautical astronomy -- Early works to 1800.; Navigation -- Instruments -- Early works to 1800.
Link to this Item: http://name.umdl.umich.edu/A40034.0001.001
Cite this Item: "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." In the digital collection Early English Books Online. https://name.umdl.umich.edu/A40034.0001.001. University of Michigan Library Digital Collections. Accessed June 14, 2025.

Pages

Page 58

CHAP. XVIII.

Having the Latitude of the place, and the plains declination, to finde the plains difference of Longitude.

IT must be understood, that the plain is supposed (in this work) to be alwayes erect; and that therefore for re / in-clining plains, the Latitude and declination here mentioned is meant of the new Latitude and new declination.

Two wayes to doe it.

Make ABC a right angle.

[illustration]

AB Sine of new La∣titude.

BC Tangent of new declination.

BAC is the diffe∣rence of the plains Lon∣gitude from your Me∣ridian.

Page 59

Make DEF a right angle.

[illustration]

II.

DE Radius.

EG Sine of new Latitude.

EF Co-tangent of plains new decli∣nation.

Draw GH pa∣rallel to DF.

HDE is the complement of the difference of Longitude.

Or DHE is the difference it felfe.

If this work be done for upright plains in your own Latitude, which will be needfull in far decli∣ners, then instead of the new Latitude and new De∣clination here mentioned, you are to use your own Latitude, and the upright plains Declination. The new Latitude and Declination are for re-in-clining plains.