Complex sentence: He has donated the Joel D. Heck Collection at the Wade Center, Wheaton College, a collection of letters related to Lewis, the educator, letters originally written to Dr. Heck about the experiences of former students of Lewis.
Split into simpler sentences: He has donated the Joel D. Heck Collection at the Wade Center, Wheaton College. This is a collection of letters related to Lewis and originally written to Dr. Heck about the experiences of former students of Lewis.