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

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                                Of ye Plummet 
The chief use thereof is to set ye dyall 
Horizontal. But yt is not ye only use; for
by and thereof, ye dyal will serve for any
place of ye Kingdom etc. to give ye true hour 
by ye shadow of ye Axis, thus. Make ye 
perpendicular-line, wch ye thred and plumet 
represents, Radius, and thereto, on ye meridi 
an-line, graduate a Tangent-line of ye 
Difference of latitude each way, beginning 
from ye foot of ye Perpendicular, and num 
ber it wth ye Latitude: then on a Plain 
exactly horizontall elevate ye North or 
South-side of ye Dyal, by help of a Screw 
in ye extremity of ye meridian-line, till ye 
Plummet hang over ye Latitude respecting:
The Scale mentioned is placed apart in this 
Dyall, and may be transferred by Compasses 
ye Dyall being almost finisht by M. Sutton 
and yt Scale [illegible] omitted.
Of ye Lunary Circle 
It is placed next within ye Projection, and 
numbred from 1 to 29, for ye days of ye 
Moons age, wth a scale of <s>1200<\s> twice twelve 
houres annext to it. If ye Moons age be recko 
ned amongst ye Days, iust against it in the 

                            
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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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