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

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                                or Cotangent of ye Latitude may be 
easily, as a Sine, transferred into ye limb
or mitagurd (?) on ye Sines; and ye Arch 
correspondent thereto taken in ye limb; for 
in any one Latitude, there is reqred no more 
Tangent-points, in this general work, but 
one. More over ye Line of Sines, if it be of 
yesame Radius, as ye Sines on the side of ye 
first Quadrant, in ye Book of Quadrants, 
serves most easily, wth ye printed Scale trea 
ted off in pag. 195. to give ye hour and azimuth 
all over England.
But ye Describer does not esteem these 
Instrumental Conclusions worth mentioning; 
his Design then being an Improvements of Points 
so as to lessen ye Charge of Instruments.

The Antiquity and Demonstration of 
Projection.
If we consider, that the Azimuths and 
Altituds have such Habitude and relaon to 
ye Axis of ye Horizon, as ye Houre Circles 
and Paralels of Declinaon have to ye Axis 
of ye Sphere, we shall find, yt whether ye 
Eye be at ye Nadir or Role-Point, ye 
Projection will be altogether yesame thing.
                            
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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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