twenty-seven-and-a-half

Updated: June 15, 2025

But it was R. C. Carrington who, by his continuous observations at Redhill, in Surrey, established the remarkable fact that, while the rotation period in the highest latitudes, 50 degrees, where spots are seen, is twenty-seven-and-a-half days, near the equator the period is only twenty-five days.

George Forbes - History of Astronomy