He served as director of the Stonyhurst College Observatory and contributed to the study of the Sun, including through observing solar eclipses.

He later taught mathematics and science at Stonyhurst, before training for the priesthood at St. Beuno's College in North Wales, leading to his ordination in 1892.

[1][3] Cortie returned to Stonyhurst to teach, and spent the rest of his life serving the college.

He studied the correlation between magnetic storms on the Earth and sunspots, eventually arguing that effects produced by the Sun, and associated with sunspots, extended outwards from the Sun in various directions and sometimes caused terrestrial magnetic storms.

[1] He became director of the Solar Section of the British Astronomical Association following the death of Elizabeth Brown in 1899, and served until 1910.