Died: 14 July 1943 in Glasgow, Scotland

John McWhan's father was John McWhan (born in Castle Douglas, Kirkcudbrightshire about 1854) who was Headmaster of Cambuslang School. His mother was Maggie McWhan (born in Ireland about 1855). He had an older brother Andrew (born about 1881) who went on to study medicine.

John McWhan attended Whitehill School, Glasgow. After winning a bursary to attend Glasgow University he studied there and was awarded an M.A. with First Class Honours in Mathematics and Natural Philosophy in 1907. He was awarded a George A Clark Scholarship which enabled him to undertake research in physics at the University of Göttingen from 1907 to 1910.

In 1910 McWhan was appointed as an Assistant in Mathematics at Glasgow University. He became a Lecturer in Mathematics in 1913, a post he held until his death in 1943. He was a member of the Edinburgh Mathematical Society, The Mathematical Association, and the Glasgow Mathematical Association. He joined the Edinburgh Mathematical Society in January 1908 and remained a member throughout his life. He was elected to the Royal Society of Edinburgh on 7 March 1921, his proposers being George Alexander Gibson, Andrew Gray, Robert Alexander Houstoun, James Gordon Gray.

An obituary, written by R A Houstoun, appears in the Royal Society of Edinburgh Year Book 1944, page 24. 
We give a version of this obituary at THIS LINK.

McWhan's death was reported in The Scotsman on Friday 16 July 1943:-

Death of Glasgow University Lecturer

1. R A Houstoun, John McWhan, M.A., Ph.D., Royal Society of Edinburgh Year Book 1944, 24.