Where a nonconforming use is changed to a use
permitted in the district in which it is located, it shall not thereafter
be changed from said conforming use to a nonconforming use.
Whenever there shall be a discontinuance or
cessation of any nonconforming use for a period of one year, such
nonconforming use shall be adjudged as abandoned, and the premises
can only thereafter be used in conformity with the existing requirements
of the zone or district in which said premises are located.