380 THE BEAUTIES OF NATURE CHAP, 
them even as much as 78—miles. Many 
also have central cones, closely resembling 
those in our own volcanic regions. In some 
cases the craters are filled nearly to the brim 
with lava. The volcanoes seem, however, to 
be all extinct ; and there is not a single case 
Fig. 50.— A group of Lunar Volcanoes. 
in which we have conclusive evidence of any 
change in a lunar mountain. 
The Moon, being so much smaller than the 
earth, cooled, of course, much more rapidly, 
and it is probable that these mountains are 
millions of years old —much older than many 
