T. B. Haeding. — On Occultations and Solar Eclipses. 479 



■we ( ? ) are brought in front, the points I and c to the axis of 

 projection, the polar axis coincident with that of projection, 

 and we are prepared to plot the path of the station along the 

 plane of projection through a revolution of the Earth, as seen 

 from the planet Venus. If there were no declination (if J 

 was at the equator) all the circles of latitude would appear as 

 straight lines across the Earth's disc ; at 90° (the poles) they 

 would appear as concentric circles ; between these extremes 

 they appear as ellipses more open as our declination increases; 

 at our declination of 10°, as an ellipse whose semi-major axis 

 equals the radius of the circle of latitude (not being shortened 

 by projection), and whose semi-minor axis equals the distance 

 between I and c on the axis of projection. 



We have only to do with one quarter of this ellipse — that 

 from Venus's meridian passage to her 6-liour angle. To draw 

 this quadrant is not a matter of difficulty, as the following will 

 show : — 



1. Draw a line across the diagram through c perpendicular 

 to the axis of projection. Measure from c towards the right 

 at quantity equal to radius of circle of latitude. Mark that 

 point 6. 



2. With distance c-6 in the compasses and centre c 

 describe the large quadrant from 6 downwards till it meets the 

 axis of projection ; and 



3. With distance c-l and same centre describe the small 

 quadrant, concentric with the other. 



4. Divide both by lines radiating from centre {c) into six 

 equal parts (of 15°) (hours). 



5. Through all the five points of division on the small 

 quadrant draw horizontal lines, and through those of the 

 larger one perpendicular lines. The intersection of these lines 

 marks at the same tivie the curve of the elliptical quadrant, and 

 the points of the hours from 1 to 5. These are the positions of 



? at her hour angles, as projected. 



Next we want the place of the Moon at conjunction, and 

 her path in orbit during her course between $ and the 

 Earth. 



The difference of declination (a =29-75') must be 

 measured from the same scale as before; and, as it is S., it 

 must be measured upwards from the Earth's centre on the 

 axis of projection. Mark this point ; also mark it the time 

 of c5 , which is when the Moon's centre is there. This in ? 

 hour-angle time is 2h. 45m. ; from this point and time she is 

 moving eastward and southward. We get from the " Nautical 

 Almanac " her motion in both directions, and from these plot 

 her motion in orbit. 



1. Her motion E. (E.A.) is given in time for 10m. as 19s. 

 Six of these go to an hour, o^nd 4sec. of time = 1' of arc. We 



