The Rev. Barbara J. Clarke will be installed as rector of St. Patrick’s Episcopal Church at 4 p.m. Sunday, Oct. 23. On hand to help celebrate the ceremony will be the Right Rev. Chilton R. Knudsen, bishop of Maine. Before coming to St. Patrick’s, Clarke served as interim rector of St. Augustine’s Episcopal Church in Washington, D.C., and is a former biology professor at The American University in Washington.