52 



THE POPULAR SCIENCE MONTHLY. 



best atmospheric conditions, to a broad black band visible at the 

 first glance. 



To all these characteristics must be added, of course, the ex- 

 traordinary occurrence of the gemination or doubling of the 

 canals. It is natural to suppose that, in such cases, what would 

 be seen would be the apparition of a new canal along side of an 

 old one. That, in fact, is what Schiaparelli described as occurring 

 during his earlier observations ; but, during the opposition just 

 passed (1888), he discovered that this was not a general rule, and 

 that it may happen that neither of the new canals, when a doub- 

 ling takes place, may coincide with the old one. " The identity," 

 he adds, " in the general direction and situation is then merely 

 approximative ; every trace of the former canal disappears, giving 

 place to two new lines." Both the width and the distance apart 

 of the twin canals vary in successive seasons. 



It would carry us far beyond the limits of space available for 

 this article to enter into a more minute account of Schiaparelli's 

 observation of the many anomalies and changes of appearance 

 which the canals present at different seasons and under varying 

 circumstances. Enough has been said to indicate that it would 

 be impossible to make a map which should show the precise ap- 

 pearance of the surface of Mars at any fixed period, and at the 

 same time contain a representation of all the phenomena which 

 are, from time to time, to be seen there. And it should be said, 

 because this is a matter that has been misunderstood, that Schia- 



Ordinary Appearance. 



Appearance in April, 1888. 



Changes in the Aspect of Libya. 



parelli does not intend his maps to be taken as portraitures of the 

 planet, but simply as sketches showing details of whose existence 

 there is no doubt whatever, but all of which can not be, or have 

 not been, seen simultaneously. 



And now there remain yet other remarkable circumstances to be 

 mentioned in order to complete the picture of the surface of Mars, 



