FREE BOOKS

Author's List




PREV.   NEXT  
|<   99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   114   115   116   117   118   119   120   121   122   123  
124   125   126   127   128   129   130   131   132   133   134   >>  
e.] It is not my intention to give a complete description of the various lunar features, and I mention but one other--the "clefts" or "rills," which are to be seen running across the surface like cracks. One of the most remarkable of these is found in the _Oceanus Procellarum_, near the crater-mountain Aristarchus, which is famed for the intense brilliance of its central peak, whose reflective power is so great that it was once supposed to be aflame with volcanic fire. The cleft, or crack, in question is very erratic in its course, and many miles in length, and it terminates in a ringed plain named Herodotus not far east of Aristarchus, breaking through the wall of the plain and entering the interior. Many other similar chasms or canons exist on the moon, some crossing plains, some cleaving mountain walls, and some forming a network of intersecting clefts. Mr. Thomas Gwyn Elger has this to say on the subject of the lunar clefts: "If, as seems most probable, these gigantic cracks are due to contractions of the moon's surface, it is not impossible, in spite of the assertions of the text-books to the effect that our satellite is now a 'changeless world,' that emanations may proceed from these fissures, even if, under the monthly alternations of extreme temperatures, surface changes do not now occasionally take place from this cause also. Should this be so, the appearance of new rills and the extension and modification of those already existing may reasonably be looked for." Mr. Elger then proceeds to describe his discovery in 1883, in the ring-plain Mersenius, of a cleft never noticed before, and which seems to have been of recent formation.[15] [Footnote 15: The Moon, a Full Description and Map of its Principal Features, by Thomas Gwyn Elger, 1895. Those who desire to read detailed descriptions of lunar scenery may consult, in addition to Mr. Elger's book, the following: The Moon, considered as a Planet, a World, and a Satellite, by James Nasmyth and James Carpenter, 1874; The Moon, and the Condition and Configurations of its Surface, by Edmund Neison, 1876. See also Annals of Harvard College Observatory, vol. xxxii, part ii, 1900, for observations made by Prof. William H. Pickering at the Arequipa Observatory.] We now return to the question of the force of lunar gravity. This we find to be only one sixth as great as gravity on the surface of the earth. It is by far the smallest force of gravity that we have f
PREV.   NEXT  
|<   99   100   101   102   103   104   105   106   107   108   109   110   111   112   113   114   115   116   117   118   119   120   121   122   123  
124   125   126   127   128   129   130   131   132   133   134   >>  



Top keywords:
surface
 

gravity

 

clefts

 

Observatory

 

Thomas

 
question
 
cracks
 

Aristarchus

 
mountain
 

Mersenius


noticed

 

recent

 
formation
 

Footnote

 
return
 

appearance

 
extension
 
modification
 

Should

 

occasionally


smallest

 

proceeds

 

describe

 

Description

 

looked

 

existing

 

discovery

 

Arequipa

 

Condition

 

Configurations


Surface

 
Edmund
 

Nasmyth

 

Carpenter

 

William

 
Neison
 

Harvard

 
College
 

Annals

 
observations

Satellite
 

desire

 
Pickering
 
Features
 

Principal

 

detailed

 
considered
 

Planet

 
addition
 

descriptions