Origin of Eight-Year Generating Cycle 91 



Venus from the Sun are as 1000 to 723; that the orbits 

 of both planets are nearly circular; and that in size, 

 Venus of all the planets most nearly approaches the 

 Earth, its diameter being 7630 miles as compared with 

 the 7918 miles of the Earth. 



Let Figure 24 represent the orbits of Venus and the 

 Earth, the orbits being assumed, for the sake of sim- 

 plicity, to be circles. At this stage no account is taken 

 of the inclination of the plane of the orbit of Venus, 

 which will be considered later on. The following simple 

 description of when and where the two planets are in 

 conjunction is given by R. A. Proctor in his Transits of 

 Venus: 



" Imagine that a straight pointer from the Sun to 

 Venus, extending to the Earth's orbit, Hke the line 

 SVE, is carried round S as a central pivot by the 

 motion of the planet Venus. Then whenever this 

 pointer comes up to the Earth, the three bodies — 

 Sun, Earth, and Venus — are in conjunction. Now, 

 Venus travels with a mean motion of 96' 7".8 per day 

 around the Sun (completing a revolution in 224.701 

 days), while the Earth travels with a mean motion 

 of 59' 8".3 (completing a revolution in 365.257 

 days); so that in each mean solar day Venus gains, 

 on the average, 36' 59".5 upon the Earth. This 

 is the rate at which our imaginary pointer, starting 

 from a position such as SVE, sweeps onwards from 

 the advancing Earth, so as to again reach the Earth 

 by overtaking it, just as the minute-hand of a clock, 

 after being in conjunction with the hour-hand, 

 passes on towards its next conjimction, with the 

 excess of its motion over the hour-hand. We have 



