118 UNIVERSITY OF MISSOURI BULLETIN 



The temperature at the surface of any one of the planets 

 which lie comparatively close to the sun such as Mars, the 

 earth and Venus, depends largely on the amount of heat 

 which they receive from the sun. Since Mars is farther from 

 the sun than the earth is, it receives less heat from it, in 

 fact less than half as much in proportion to its area. From 

 this fact the average temperature on Mars has been estimated 

 at 33 F, a temperature which I suppose is too low to 

 admit of the origin and continued existence of many of the 

 forms of life we have on the earth. However, this estimate 

 of the temperature is really very uncertain. 



As for the direct evidence, not merely of the possibility, 

 but of the actual presence of life on Mars, Mr. Lowell pro- 

 fesses to have observed on the surface of the planet a large 

 number of curious fine lines which have been called canals, 

 and which he believes to be real irrigating ditches, constructed 

 artificially by the intelligent inhabitants. These lines are 

 said to be in the form of great circles on the sphere of the 

 planet, and it is argued that nature would not herself form 

 surface markings of such geometrical simplicity. Many of 

 the best observers, however, fail to see anything like the dis- 

 tinct and clear lines which Mr. Lowell maintains that he can 

 see. There certainly are surface marks there, but a planet 

 as seen through a telescope is never a very distinct object, and 

 it is natural that different observers should differ largely as 

 to just what they see. Lowell thinks that his telescope is an 

 exceptionally efficient one, and that the location of his observ- 

 atory in the dry climate of Arizona is more free than any 

 other location from those atmospheric disturbances which 

 interfere so much with telescopic vision. I am inclined to 

 think that the case for the habitability of Mars is not proven, 

 and that the evidence is rather against it. 



Limits of Stellar Space. One of the questions which 

 astronomers are called upon to answer is this : Are there any 

 limits to the positions of space occupied by the stellar universe, 



