William James Stewart Lockyer (3 January 1868 – 15 July 1936) was an English astronomer and physicist. His work included studies on sunspot cycles and is remembered for what is now known as the Brückner-Egeson-Lockyer cycle.
William was the fifth and youngest son of Sir Norman Lockyer. He was educated at Cheltenham; Trinity College, Cambridge; Royal College of Science, London; and Göttingen. His doctoral work of 1896 was on the variable η Aquilae. He worked with his father initially examining sunspot periodicity and weather correlations. He then travelled around the world following eclipses from 1896 to 1932. He was involved in the establishment of the International Meteorological Committee. In 1920 he succeeded his father as director at the newly renamed Norman Lockyer Observatory in Sidmouth. Lockyer was known for his work on sunspot cycles.
He married Kate Irene in 1921.
- Lockyer, W.J.S. (1901). "The solar activity 1833-1900". Proceedings of the Royal Society of London. 68 (442–450): 285–300. doi:10.1098/rspl.1901.0047. ISSN 0370-1662.
- Lockyer, N.; Lockyer, W. J. S. (1900). "On solar changes of temperature and variations in rainfall in the region surrounding the Indian Ocean". Proc. R. Soc. 67: 409–431. doi:10.1098/rspl.1900.0045.
- "William James Stewart Lockyer". Monthly Notices of the Royal Astronomical Society. 97 (4): 275–277. 1937. doi:10.1093/mnras/97.4.275a.
- Wilkins, G. A.; Wilson, C. M. W. (1997). "The contributions of Norman and James Lockyer to meteorology". Weather. 52 (9): 276–282. doi:10.1002/j.1477-8696.1997.tb06324.x.