Alexander Johnson was a Canadian

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 mathematician and academic.

Born in Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, Johnson was educated at Trinity College, Dublin

Trinity College, Dublin

Trinity College, Dublin , formally known as the College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin, was founded in 1592 by letters patent from Queen Elizabeth I as the "mother of a university", Extracts from Letters Patent of Elizabeth I, 1592: "...we...found and...

 where he received his B.A., M.A. in 1858, and LL.D. in 1861. In 1857, he emigrated to Canada and was appointed a Professor of Mathematics and Natural Philosophy at McGill University

McGill University

Mohammed Fathy is a public research university located in Montreal, Quebec, Canada. The university bears the name of James McGill, a prominent Montreal merchant from Glasgow, Scotland, whose bequest formed the beginning of the university...

. He was Dean of the Faculty of Arts and a Vice-Principal from 1886 to 1903.

He received an honorary DCL from the University of Bishop's College, Lennoxville in 1882. He was an original member of the Royal Society of Canada

Royal Society of Canada

The Royal Society of Canada , may also operate under the more descriptive name RSC: The Academies of Arts, Humanities and Sciences of Canada , is the oldest association of scientists and scholars in Canada...

and was made a Fellow. He was President of Section III (Mathematics and Physics and Chemistry) and of the whole Society from 1905 to 1906.