310 NATURE-STUDY REVIEW 



its seasons white-caps appear about its poles in Winter and disappear 

 in the Summer, and are therefore generally supposed to consist of 

 ice. Lowell mapped many lines on Mars which are called canals; 

 these canals have been seen by others to a lesser extent, but all 

 astronomers do not agree with Lowell that the canals were the 

 result of the labors of creatures of intelligence. There is a dark 

 area extending across the face of Mars called the Hour-g 1 ass Sea, 

 for it was once supposed that this dark area was water. Now we 

 know that it is rock or land of a different color, and is probably a 

 desert. Mars has two little moons named after the mythical steeds 

 which drew the chariot of the War-god, Mars. They are the tiniest 

 little moons that we know about, Phebos being only 36 miles in 

 diameter and Deimos only 10. Deimos moves around Mars in 

 about 30 hours while Phebos "does his whirl" in about 1^2 hours 

 which makes the shortest month that we know anything about. 



Mars may be seen during this month in the southwest in Capri- 

 cornus, it can be easily found as a red glowing star south of Altair. 



To the beginner of star study the morning and evening stars are 

 a pu?zle; and indeed, unless one has a knowledge of the higher 

 mathematics, the movements of our sister planets seem most 

 mysterious. Why and how do they change from morning to evening 

 stars and from evening to morning stars ? There are just a few facts 

 that we may remember, and perhaps if we have a diagram, we 

 may understand them. Take for instance the movement of Venus 

 when it is on the west side of the sun, it naturally rises earlier than 

 the sun, and therefore we see it as a morning star. When it is on 

 the east side of the sun we can easily understand that it sets later 

 than the sun and is therefore an evening star. When it is behind 

 or directly between us and the sun, we cannot see it at all, and it is 

 therefore passing from an evening to a morning star, or from a 

 morning to an evening star and is lost in the light. 



There are a few terms, which, if mastered, will make the astro- 

 nomical news given us in periodicals much more intelligible. When 

 one of the planets whose orbit lies between ours and the sun is on 

 the same side of the sun as we and nearly in line with us and the 

 sun it is said to be in "inferior conjunction," when it is on the far 

 side of the sun from us and nearly in line with it and us, it is said 

 to be in "superior conjunction." But if a planet whose orbit is 

 outside of ours is on the far side of the sun nearly in line with us 

 it is merely said to be in "conjunction" and is of course farthest 



