Till-. MOON'S 55 



ittte to about three miles and a quarter. Horachel 



problem, armed with u t. leacope of six 



feet eight inches focal length, which he speak* of aa 



"a very excfll.-n- u.il to any that wan 



I-N.T i.i i-i. II I .u"l,l l. ;! .J-.. l! 



mon diligence an <-h made op in 



measure for the ini|Mrfrct iii.striiiui'iit.s of previous 

 astronomers; .-m-l h- hi-l r.nfi<lonce in himselt 



^oodncm of the work he had 



He waa struck by the "deep shadows" east by 

 i tains on the moon's surface. Probably these 

 shadows were then a puzzle to him. But he made 

 one sagacious observnt!'! \\hirh subsequent obsei 

 have developed into a view of the moon's face alto- 

 gether different from what he started with. On Mons 

 Lactr he writes : " I am almost certain there art- 

 very considerable cavities or places \\ 

 descends below the level of the convexity, just before 

 these mount t !he moon's face is now know 



be pitted with hollows of great extent and depth. 

 s predecessors called them seas and oceans, 

 of \vhich i!i. -re are none on the moon. The hills and 

 it rise from these vast cavities do not at 

 the utmost greatly exceed the estimate come to by 

 Herschel, a mile and a half, or a mile and three- 

 limit, r> lit But if the height be reckoned 



the hollow from which they rise, it may be 

 nearer three times as much. We count the heights of 

 mountains on the i*arth from the level of the set 

 we rock* o the bottom of the ocean, our moun- 



tains will bo found considerably to exceed in height 

 those of the moon. It is now known that these 



