May, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



435 



Morning and Evening 

 Stars in 1906. 



The accompanying diagram is designed to aid in the 

 identification of the planets which rise and set before 

 the sun durint; the present year. The orbits of Mercurv, 



Mercury's position is first shown for January 3, and 

 thereafter at intervals of eight days. As this planet's 

 journey round the sun occupies 87 days and 23J hours, 

 it reaches its first position again, approximately, on 

 April I, June 28, September 24, and December 21. 

 .Since Mercury's revolutions occupy slightly less than 

 88 days, therefore after four revolutions and a small 

 fraction (352 days), the planet will reach a position 

 which is about half a degree in advance of that occu- 

 pied on January 3. But to avoid confusion the posi- 



Venus, 

 plotted 

 plancls 

 Jupilcr, 

 iimils of 

 thr.M- an 

 and that 

 of a r<'\( 

 ancc of 

 position 

 assigned 



Mars, are diagramniatici 



in as lo show iho positiojis of each of those 



at iiiter\als of eight davs. The orbits of 



Saturn, Uranus, and Xeptunc fall bovond the 



the page; but since the motions of the last 



liinil<'(l lo \vi\- small angular measurements, 



of Jupilcr is not more than about one-twelfth 



ilulion, the reader will Ih' abk', with the assist- 



the drawing, to determine ajiproximatelv the 



in the heavens of each of thes*- planets at an\- 



date. 



tions in the diagram are made identical, since for 

 practical pin-poses the position is suHiciently accurate. 

 \'<>nus performs her revolution in 224 days i6| hours; 

 and in the case of this planet, and for the purposes of 

 the diagram, 224 days is regarded as being the interval 

 which will bring the planet to its first position of 

 laiuiarv 3. Subsequent positions are shown at intervals 

 of t'ight davs. because, by their selection, they may be 

 compared with the positions of Mercury, the earth, or 

 Mars on the same dates. \'enus makes about iS re- 

 volutions in our vear; and her second revolution begins 



