Complex sentence: The tower houses a carillon that John D. Rockefeller Jr. donated in memory of his mother, Laura Spelman Rockefeller, which was installed from 1925 with additional bells later.
Split into simpler sentences: The tower houses a carillon that John D. Rockefeller Jr. donated in memory of his mother, Laura Spelman Rockefeller. It was installed from 1925 with additional bells later.