LIFE IN MARS. 12$ 



half of the planet where winter is in progress are very 

 indistinctly seen, a whitish light sometimes replacing 

 the red and green markings altogether in these regions. 

 On the contrary, the regions where summer is in 

 progress, are generally very well seen. 



The reader will infer from what has been said on 

 these points, that the study of Mars cannot be carried on 

 very rapidly by our astronomers ; for, in the first place, 

 Mars only returns to our midnight skies at intervals of 

 more than two years, and be remains but for a short 

 time favourably placed for observation. Then one 

 half of his surface only can be seen at a time, and 

 nearly one half even of that hemisphere is commonly 

 concealed by clouds, which also extend all round the 

 disc, so that perhaps but about one-eighth of the 

 planet's surface can be favourably studied. When we 

 add to these considerations the circumstance that not 

 one night out of ten in our climate or, perhaps, in 

 any is well suited for the use of powerful telescopes, 

 while even favourable nights cannot always be devoted 

 to the study of Mars (other celestial objects often re- 

 quiring special attention), it will be understood that 

 the progress of discovery has not been so rapid as, at a 

 first view, might be expected. When we are told that 

 more than two centuries have elapsed since the tele- 

 scopic study of Mars began, it seems as though ample 

 time had been given for research ; but the time which 

 has been actually available for that purpose has been 

 far more limited than that estimate would imply. 



And now, returning to the consideration of the 



