 Thus , Innis travelled extensively beginning in the summer of 1924 when he and a friend <unk> an 18 @-@ foot ( 5 @.@ 5 m ) canvas @-@ covered <unk> hundreds of miles down the Peace River to Lake <unk> ; then down the Slave River to Great Slave Lake . They completed their journey down the Mackenzie , Canada 's longest river , to the Arctic Ocean on a small Hudson 's Bay Company <unk> . During his travels , Innis supplemented his fur research by gathering information on other staple products such as lumber , pulp and paper , minerals , grain and fish . He travelled so extensively that by the early 1940s , he had visited every part of Canada except for the Western Arctic and the east side of Hudson Bay . 
