_THE MOON, CHILD OF THE EARTH AND THE SUN_ 212 The moon a favorite subject for intellectual speculation--Its nearness to the earth graphically illustrated--Ideas of the ancients--Galileo's discoveries--What first raised a serious question as to its habitability--Singularity of the moon's motions--Appearance of its surface to the naked eye and with the telescope--The "seas" and the wonderful mountains and craters--A terrible abyss described--Tycho's mysterious rays--Difference between lunar and terrestrial volcanoes--Mountain-ringed valleys--Gigantic cracks in the lunar globe--Slight force of gravity of the moon and some interesting deductions--The moon a world of giantism--What kind of atmospheric gases can the moon contain--The question of water and of former oceans--The great volcanic cataclysm in the moon's history--Evidence of volcanic and other changes now occurring--Is there vegetation on the moon ?--Lunar day and night--The earth as seen from the moon--Discoveries yet to be made.