The Earth's Other Motion

The Earth's Other Motion.

The earth, in addition to its diurnal and annual revolutions, has a slow wabbling of its axis, a motion seldom mentioned even in the textbooks of astronomy. This curious motion may be properly likened to that imparted to a top by touch of the finger on its rim when it is in rapid movement, the touch causing the upper end of the top's stem to describe a small circle. So, too, the mighty sun lays hold of the rim of the great terrestrial top, and it begins to oscillate in the long period of 21,000 years-that is to say, on Dec. 21, 1248, the earth made its nearest approach to the sun, and it will approach equally near in 10,500 years from that time, or on the 21st day of June in the year 11,748. This has all to do with climate both north and south of the equatorial line.

In the period comprising the first our northern winters are short and mild and our summers are long and sunny. But during the period of which the year 11,748 will be the middle our winters will be awful in their severity and our summers short and cool. Even now the northern hemisphere is slowly but surely losing its long, sunny summers, and if you should live until the winter of the year 11,748-49 you could tell a story of cold and snows that would pale to insignificance the stories of the cold winter of 1833-34, for the whole northern hemisphere will then be in the midst of its great and terrible winter.