Hello,
There are two sources:
1. In the church record of his marriage to Margaret Ryan (4 Nov 1856), he is identified as "Cornelius Harrington, of the Rail Road in this mission"
2. A "Missing Friends" advert in the Boston Pilot (7 Jan 1871):
"OF CORNELIUS HARRINGTON, son of Timothy Harrington and Julia Falvey, from Rosnagrena, Top of the Glen, Glengariffe, county Cork; he got married to Mike Hyan's [Ryan's] daughter, from Cappawhite, county Tipperary, about 12 years ago, at Guaranacque [Ganonoque], Grand Trunk Railroad, Canada. If this should meet his eye, or any person acquainted with him, they will confer a favor on his uncle by writing to him. Address Jeremiah Falvey, Moira, Franklin co., N.Y."