He discovered or co-discovered a number of comets, including periodic comets 43P/Wolf–Harrington, 51P/Harrington (discovered in 1953), 52P/Harrington–Abell (discovered jointly with George Ogden Abell in 1955) and the comet/asteroid 107P/Wilson–Harrington, which he and Albert Wilson discovered in 1949 and which had become an asteroid by 1988.
Otkrio je ili suotkrio više kometa, među njima periodične komete 43P/Wolf-Harrington, 51P/Harrington (otkriven 1953.), 52P/Harrington-Abell (otkrio ga skupa s njime George Ogden Abell 1955.) te komet/asteroid 107P/Wilson-Harrington, koji su on i Albert Wilson otkrili 1949. i koji je postao asteroidom do 1988. godine.