He had a distinguished career as educator, researcher, and activist in science and society, but he is increasingly well known for his pioneering paper [1] in 1947 on the band structure of graphite, and particularly graphene,[2] the subject of the 2010 Nobel Prize in Physics.

[3] Advised by L. J. Synge, then head of the Applied Mathematics Department at Toronto, to hold himself ready for war work in Canada, Wallace took a two-year job at the University of Cincinnati and then moved to a lectureship at MIT.

From 1943 to 1946 Wallace worked as one of an impressive group of theorists and mathematicians led by George Placzek on nuclear reactor fundamentals, including study of the effects on graphite and other materials of intense neutron and ion bombardment.

[1] When the Montreal effort moved to the Chalk River site in 1946, Wallace joined the Mathematics Department at McGill University and began to build a group of young theoretical physicists there.

The anomaly, at least in North America, of theoretical physicists in the Math department, not in Physics, had historic roots at McGill, dating from Ernest Rutherford's time.

He has documented the post-war story of the growth of a tiny number of isolated theoretical physicists in Canada, basically "outsiders," into a viable community of "insiders," not only at McGill.

[5] Initially working in nuclear physics and properties of graphite, in the mid-1950s Wallace turned his attention to the newly discovered positron annihilation in solids and liquids.