Slingsby is perhaps most famous for being the first on Storen, or Store Skagastølstind ( in 1876, the third highest mountain in Norway. It was considered impossible to climb then, but Slingsby defied popular notion and climbed the mountain, for the last part alone. Slingsby also attempted to climb the 1392metres tall and highly steep Stetind in Narvik, but his attempt ended up as a failure, as he never made it to the peak of the mountain. Slingsby would later describe this mountain as the ugliest one he had ever seen.