John Bulmer Rutherford in "Onward Dear Boys: A Family History of the Great War"

I had a quick look at Onward Dear Boys by Philippe Bieler, McGill-Queen's University Press, 2014.  This book reprints a letter written by Andre Bieler during WWI, in which he mentions seeing his friend John Bulmer Rutherford.

Here's a blurb of the book from the McGill-Queens' University Press Website.

"The Bieler family's vast collection of wartime letters and photographs tell intimate, firsthand stories of five young brothers and their parents. In Onward, Dear Boys, Philippe Bieler skilfully weaves together his own voice with those of his grandparents, his father, and his uncles into a story of war, immigration, and family life.

Settling in the province of Quebec, then divided into French-speaking Catholics and English-speaking Anglicans, was a struggle for these devout, francophone Calvinists, but with the unexpected declaration of war in 1914 came an even greater challenge. In 1915 three of the five Bieler boys volunteered with the Princess Patricia Regiment, and in 1916 the fourth son followed. The eldest, Jean, became an assistant to Colonel Birkett, commander of the McGill-financed Canadian Hospital in Boulogne, and the second-eldest, Etienne, was promoted to lieutenant of an artillery brigade. The other two were privates who fought in battles including Sanctuary Wood, the Somme, Vimy, and Passchendaele, and in 1917, the fourth son, Philippe, died at the front. Upon their return to civilian life, the surviving brothers became leaders in government, science, and the arts : the eldest as Deputy Finance Director of the League of Nations, the second as a colleague of Sir Ernest Rutherford in the research of the atom, and the third as President of the Federation of Canadian Artists. The youngest, Jacques, who was too young to go to war, was an instigator of the CCF party, a precursor to the NDP.

Enlivened by a wealth of family archival material, Onward, Dear Boys is a poignant story of the experiences of war and its impact on a family of new Canadians during the first decades of the twentieth century."

Andre Bieler, who wrote the above letter, was a well-known artist who lived in Montreal for many years and was later connected to Queen's University.  Click here to see his bio in the Canadian Encyclopedia.