Complex sentence: The cathedral was consecrated on June 18,1873, by Bishop Lee who was joined by Bishops Robert Clarkson of Nebraska and Henry Benjamin Whipple of Minnesota, who preached the dedicatory sermon.
Split into simpler sentences: The cathedral was consecrated on June 18,1873 by Bishop Lee. He was joined by Bishops Robert Clarkson of Nebraska and Henry Benjamin Whipple of Minnesota, who preached the dedicatory sermon.