The Third Book of the CrossStaffCHAP. IV.

Latit.  51  30  
Ho.  Ang. Po.  Arc. Po.  
Gr.  M.  Gr.  M  
12  0  0  0  0 
3  45  2  56  
7  30  5  52  
11  15  8  51  
1  15  0  11  50 
18  45  14  52  
22  30  17  57  
26  15  21  6  
2  30  0  24  20 
33  45  27  36  
37  30  31  9  
41  15  34  28  
3  45  0  38  3 
48  45  41  45  
52  30  45  34  
56  15  49  30  
4  60  0  53  35 
63  45  57  47  
67  30  62  6  
71  15  66  33  
5  75  0  71  6 
78  45  75  45  
82  30  80  25  
86  15  85  13  
6  90  0  90  0 
Extend the Compasses from the Sine of 90 gr. to the Sine of the Latitude; so the same Extent shall reach from the Tangent of the Hour, to the Tangent of the Hourline from the Meridian. Thus the Latitude being 51 gr. 30 m. I extend the Compasses from the Sine of 90 gr. to the Sine of 51 gr. 30 m. and find the same extent to reach from the Tangent of 3 gr 45 m. unto the Tangent of 2 gr. 56 m. for the distance of the first quarter from the Meridian; and from the Tangent of 7 gr. 30 m. unto the Tangent of 5 gr. 52 m. for the half Hour; and from the Tangent of 11 gr. 15 m. to the Tangent of 8 gr. 51 m. for the third quarter; and from the Tangent of 15 gr. 0 m. unto 11 gr. 50 m. for the first Hour; And so the rest, as in the third Column of this Table, under the Title of the Arks of the Plane.
Only when I come to set one Foot of the Compasses to 48 gr. 45 m. for the finding of a quarter past 3, the other Foot will fall out of the Line, and then I may either take out so much as is out of the Line beyond 45 gr. and turn it back into the Line, and it will reach from 45 gr. to 41 gr. 45 m. or I may use cross work, extending the Compasses from the Sine of 90 gr. to the Tangent of 48 gr. 45 m. so the same extent will reach from the Sine of 51 gr. 30 m. to the Tangent of 41 gr. 45 m. And such is the distance of the Line of 3 Hours ¼ from the Meridian.
This done, I come to the Plane, and there according as the Lines do fall in the Fundamental Diagram,
The Line belonging to the Hour of 6 will be perpendicular to the Meridian, and the Hourlines before 6 in the Morning, or after 6 in the Evening, may be supplied by continuing their opposite Hourlines beyond the Center, as the Hourline of 7 in the Morning continued, will be the Hourline of 7 in the Evening: And so the rest.
Lastly, I set up the Style over the meridian, so as it may cut the Plane in the Center, and there make an Angle with the meridian equal to the latitude of the Place; so it shall represent the Axis of the World, and be truly placed for casting of the Shadow upon the Hourlines in an Horizontal Plane.
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