THE HAMILTON ASSOCIATION. 101 
Now let us consider particularly the evidences of physical 
life on the Moon’s surface. By physical life I mean changes 
due to internal or external heat, such as volcanic action or 
earthquakes, the formation of snow or the disintegration of 
lofty peaks. - On the Moon heat cannot produce the grand 
phenomena we are accustomed to on earth. No ~201ng cata- 
racts pour down its rocky heights; no mountain streams brawl 
to the plains beneath; no placid rivers roll through fertile plains 
to join the heaving sea; no furrowed waters lash the shores of 
its wide snread oceans; no clouds obscure the heavens or tra‘ 
grateful shadows over the lunar plains; no blinding snow 
storms can ever sweep the land, or gentle rain revive the 
parched soil. On the Moon all is barren rock and arid dust. 
Here a volcano may be puffing up ashes and vapors, but no 
winds will scatter them abroad. In the most active volcanic 
regions no hot springs will bubble up from Plutonian realms. 
Dry water van-~ or pieces of hot ice at most, would be the 
lunar equivalent for a terrestrial gevser. Perhaps a seismo- 
graph might indicate tremors every now and then, shaking the 
rocky frame of our satellite, and every now and then toppling 
down some crag or opening up new cracks in her crusts. Per- 
haps, too, a Pelee sometimes there explodes harmlessly over un- 
inhabited wastes and remakes itself for the benefit of prying 
human eyes. 
What evidence have we of changes such as these? Linne 
is the classic example. 
W. H. Pickering speaks thus of Linne: “Earlv in the last 
century Lohrman described Linne as being very deep, and as 
over four miles in diameter. Maedler observed it seven times, 
and described it as very distinct under the oblique illumination 
of the sun, when the contrast of shadow was strongest, and as 
measuring six miles in diameter. Schmidt drew it eight times 
and represented it as being seven miles in diameter and one 
thousand feet deep. Schmidt, in 1842 was the last astrono- 
mer, apparently, to see it with any such dimensions, and in 1866 
he announced that it had disappeared. A few months later, 
however, he found in its place a small “craterlet” about one 
