A WHEWELLITE ESSAY ON MARS. 1 55 



a great mass of ice had slipped away, leaving an inter- 

 vening dark space, which in a few hours was snowed 

 over, the gap remaining thereafter invisible ? No other 

 explanation, indeed, seems possible. But how tre- 

 mendous a catastrophe to be discernible from a station 

 some forty millions of miles away ! Granting even 

 that Mitchel used a power of 1,200 (which we find 

 given in Loomis's Practical Astronomy as the highest 

 power of the Cincinnati telescope), Mars was still 

 viewed as from a distance of 40,000 miles with the 

 naked eye. Let any one who has observed the aspect 

 of an Alpine region, as seen with the naked eye from a 

 distance of forty miles (that region being known, so 

 that he could estimate the degree by which distance 

 reduced even the most imposing mountain features), 

 consider what would be the effect of removing the 

 point of view to a distance one thousand times greater. 

 Not merely a mountain-range, but a whole country 

 would be invisible at such a distance. But add to 

 these considerations the fact that the most stupendous 

 mountain catastrophes are reduced apparently to utter 

 insignificance at a distance of a few miles, and are 

 altogether undiscernible at a distance of thirty or forty 

 miles, and we shall be able to understand, though we 

 remain utterly unable to conceive, the vastness of the 

 catastrophe on Mars, the effects of which could be 

 discerned when viewed as by the naked eye from a 

 distance of 40,000 miles. One would imagine that the 

 very frame of the small planet must have been shaken. 

 It does not appear to us altogether unlikely that the 



