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 ...
About this Item
Title
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 ...
Author
Castlemaine, Roger Palmer, Earl of, 1634-1705.
Publication
London :: Printed for Joseph Moxon ...,
1679.
Rights/Permissions
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Subject terms
Astronomy -- Early works to 1800.
Globes -- Early works to 1800.
Link to this Item
http://name.umdl.umich.edu/A31232.0001.001
Cite this Item
"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 ..." In the digital collection Early English Books Online. https://name.umdl.umich.edu/A31232.0001.001. University of Michigan Library Digital Collections. Accessed June 3, 2024.
Pages
OPERATION XXXI. How to make an Horizontal Concave Dial by the Globe, and Geometrically also.
COmpose so your Globe in the Concavity given (suppose* 1.1 BAC in Scheme 37.) that A the Center of the said conca∣vity shall concurr with the Center of the said Globe; then drawing your String over each necessary hour Circle on the Globe to the sides of the Concavity, mark as many Points, as shall be conve∣nient for the Describing the corresponding hour Circles, and the Pin (AD) erected in the Nadir at D as high as the said Center A, I mean a Pin equal to the Semi-diameter of the Concavity, will with its Top always show you the hour.
Tho the former way be impracticable when the Hole is less* 1.2
descriptionPage 114
than the Globe, yet it serves to illustrate and make easy the Geo∣metrical Operation; for you have nothing (you see) to do, but to draw hour Circles within as you would without, were the said Concavity a whole Sphere, and then the Top of its Semi-Diameter (i. e. the poynt which lyes in the Center A) will perform the Stiles* 1.3 part; for since the Sun is every Hour (as we have before showd you) in the same Plane of the true hour Circle, and since A the Top of the Semi-Diameter (being in the Center of the Concavity,) is part of the Axis (or Common Section of all the Hour-Circles) it follows, that its Shadow must fall on the true Hour.