COMSTOCK OUR OWN SUN AND HIS OWN FAMILY 309 



miles, and it is only about half the size of the earth, and its year is 

 about 687 days long; its orbit is more eccentric than is ours. The 

 late Percival Lowell made a careful study of Mars and his book 

 on the subject is most interesting reading. Mars receives less than 

 half as much light and heat from the sim as does the earth ; because 

 its orbit is so eccentric it is nearer to us when in opposition some 

 years than others. The last week in August in 1924 it will be as 

 near to us as it ever can be, and we hope that many observations 

 will be taken. Professors McFee and Todd are planning to photo- 

 graph it from the bottom of a mine shaft in Chili so that the photog- 

 raphy can go on during the daytime; they will use a very large 

 telescope. Some astronomers do not have much faith in this under- 

 taking, but let us hope that they will succeed. Mars has a day 

 about 24>^ hours long and its axis is inclined to its orbit plane 

 similar to that of the earth; its seasons corresponding to our own. 



Mars, Showing the Double Canals. After a drawing made 

 at the Lowell Observatory. 



but are twice as long since it has so far to travel because of the 

 length of its yearly path ; its force of gravity is about four-tenths 

 that of the earth. It has an atmosphere and during thechange^of 



