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

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                                That this Projection will serve to beget
ye Analomina or Gnomonick Projection etc.
and to describe ye Conick Sections therein.
By setting off each distance from ye Center to 
any Parallel in any Azimuth, in a Sine or single 
Tangent respectively, of yesame Ark, whereof 
ye Index, as it is numbred gives ye complemt 
of ye half Ark, and by this means also find 
innumerable Points in a great Circle of ye 
Sphere, when it falls too great for a pair of 
Compasses to describe; from it may be deri 
ved easy Demonstraons of ye D Napiers 
Prop. To find an Angle, when 3.sides in a 
Sphericall Triangle are given; Or, both ye 
other Angles, at 2.opaons; When two sides 
wth ye Angle comprehended are given (wch occasion 
ned  M. Oughtreds Trigonometry). A method for cal 
culatg Trigonometrically ye lengths of ordinates 
falling from ye Intersections of any of ye Conick 
Sections on ye Axis of those figures. An easier 
method of findg ye Latitude and Declinaon, by having 
3.altitudes of ye Sun, and ye differences of Azimuth 
given, and some other Prop<sup>s<\sup> of like nature.
Nov. 7<sup>th<\sup>. 1667.
by Mr J Collins 
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John Collins
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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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