Quote by Maimonides
For the elements have the property of moving back to their place in a straight line, but they have no properties which would cause them to remain where they are, or to move other-wise than in a straight line, These rectilinear motions of these four elements when returning to their original place are are of two kinds, either centrifugal,vziz.
Summary
This quote explains that the four elements have the tendency to move straight back to their original position. However, these elements lack any properties that would make them stay in their current position or move in any other way than in a straight line. The quote also mentions that there are two types of rectilinear motions when the elements return to their original place: centrifugal and another type that is not further specified.
By Maimonides