104 THE WORLD. 



this line, altering its position in space; but amidst all these 

 changes, the line of the apsides knows no change. Its length 

 remains the same notwithstanding all the perturbations of the 

 planets % and all the changes to which the rest of the orbit may be 

 subjected. The eccentricity of the earth's orbit is now slowly 

 changing, diminishing at the rate of about 11" in a century, on 

 account of the mutual gravitation of the planets. It will continue 

 to diminish for centuries, and it is somewhat curious that this 

 dimunition is indicated by the movements of the moon, for it 

 produces, as we have remarked before, no effect upon the period- 

 ic time of a revolution of the earth. It is now pretty well deter- 

 mined that the motion of the moon is continually accelerated. 

 Upon comparing observations made at distant intervals, it is found 

 that the Chaldean and Alexandrian observations give a longer 

 period, than the Alexandrian and Arabian of the eighth century; 

 and a comparison of the Arabian and modern observations, gives a 

 still shorter period. These variations are all periodical, and are 

 compensated in opposite points of every period, the mean distan- 

 ces, and mean periods, will always remain the same. "Cold, 

 we think, must be the heart that is not affected by this mark of 

 beneficent wisdom in the contriver of the magnificent fabric." 



