Early English Books Online

Previous Section Next Section

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 23, 2025.

Pages

CHAP. XIII.

How to draw upright declining Dials when the Latitude of the place is very little or very great.

IN the work of the 10 Chap. it may fall out that either the Tangent or co-tangent of the Latitude may be too great, such as the Scale wil not afford.

Page 43

This will frequently fall out in the new Latitude of re-in-cliners: to remedy that inconvenience, I have added these helps.

Where the Latitude is but small

[illustration]

  • A rectangle parallelo.
    • 1. AB=CD=tang. of Latit.
    • 2. BD=AC=Radius.
  • 3. BE=CG=Sine declination.
  • 4. A12=EF=cosine of declination.
  • 5. AH=consine of Latitude.
  • 6. H m♒AB.
  • 7. Draw EG, it will cut CD in K. AK is the line of six: it cuts H m at 6, make A6=A6, on both sides, and draw 12 6; 12 6; and divide them as the other are in the 10 Chap.

Page 44

Or you may draw BC the Diagonall, and EK ♒ thereto, and so omit CG.

Or you may make the ∠DEK=to your Latitude, and so omit the two former.

Or thus.

After the 1, 2, 3, 4, 5, you may omit the 6. Then 7thly. Draw EG it will cut CD in K, and AK is the line of six.

Then lay a Ruler from 12 to H, cutting DC in L.

Make 12M=CL, and AN=AK.

So shall KM, MN, be ♒ to the two former lines 6 12; 6 12; and may supply their Offices som∣what better, because they are larger.

Where the Latitude is great.
  • a rectangle parallelogr.
    • 1. AB=CD=Radius,
    • 2. BD=AC=co-tang. lat.
  • 3. BR=CG=Sine declination. GR a right line cutting DB in E. AE Substilar. AG houre of 6.
  • 4. GP=RT=A12=co-sine of declination. TP a right line, cutting BD in O. AEF a right angle.
  • 5. EF=EO. AF the Style.
  • 6. AH=co-sine Latitude.

Page 45

  • Hm♒AB, cuts AG in 6. A6=A6, on both sides. Draw 6 12; 6 12, &c.
    [illustration]
    Or after the 1, 2, 3, 4, 5.
  • 6. Draw 12 H, it cuts DC in L. Make 12 M=LC: and AN=AG. Then GM, MN shall be ♒ to 6 12; 6 12: and may therefore supply their uses.
Do you have questions about this content? Need to report a problem? Please contact us.