Description of the double horizontal dial presented to the Royal Society by John Collins

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                                peep by ye thred, moving it to and fro 
on ye Dyal, till you can see one of those 
Stars in yesame plaine wth ye Thred and 
ye Axis of ye Dyall; then does ye Thred on 
ye Dyal give you ye Stars houre , whereto 
adding ye Stars Adscension, and ye Complemt 
of ye Night, as is shewd in ye Sector on a 
Quadrant pag. 32.
Of ye Line of Tangents and Sines 
issuing from ye Center.
The Line of Tangents is no other, than ye 
usual Index of ye Projection, numbred like
wise wth ye single Arks from ye Center, and 
thereby becomes a true natural Tangent of 45
The Line of yo <sup>d<\sup> of Sines issues likewise from 
ye Center, and is also numbred like a Line of 
versed Sines, and is so placed, as to be at ye 
beginning of a Quadrant of ye Limb. <s>The <\s>
The joint use of these is, to find ye Hour 
and Azimuth of ye Sun universally, wth ye 
aid of Compasses, as is shewd in ye Sector on 
a Quadrant p. 100.101. But <u>there<\u> a Tangent 
of 45<sup>d<\sup> runs through ye Limb; whereas <u>here<\u> 
it issues from ye Center. But ye Tangent 
                            
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Manuscript details

Author
John Collins
Reference
CLP/24/6
Series
Cl.P
Date
1667
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Description of the double horizontal dial presented to the Royal Society by John Collins, 1667. From The Royal Society, CLP/24/6

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