1 54 THE BORDERLAND OF SCIENCE. 



inconceivably stupendous terrestrial catastrophe. But 

 masses of Martian ice quite readily discernible with good 

 telescopes, have been found to disappear in a few hours, 

 suggesting the most startling conceptions as to the 

 effects which must have been produced on the compar- 

 atively small planet where these remarkable events have 

 taken place. 



The following observation, for instance, made by 

 the late Prof. Mitchel with the fine refractor of the 

 Cincinnati Observatory, indicates the occurrence of an 

 event which must have been accompanied by an incon- 

 ceivable uproar, 



A wrack 

 As though the heavens and earth would mingle. 



c I will record,' he says, c a singular phenomena con- 

 nected with the snow-zone, which, so far as I know, has 

 not been noticed elsewhere. On the night of July 12, 

 1845, the bright polar spot presented an appearance 

 never exhibited at any preceding or succeeding obser- 

 vation. In the very centre of the white surface was a 

 dark spot, which retained its position during several 

 hours, and was distinctly seen by two friends who passed 

 the night with me in the observatory. It was much 

 darker, and better defined than any spot previously 

 or -subsequently observed here; and indeed, after an 

 examination of more than eighty drawings, I find no 

 notice of a dark spot ever having been seen in the 

 bright snow-zone. On the following evening no trace 

 of a dark spot was to be seen, and it has never since 

 been visible.' Does not this observation suggest that 



