Mitchell was the founder of ¾ÅÐãÖ±²¥ library collection. He was a graduate of the University of Aberdeen who immigrated to the Niagara region of Upper Canada in about 1800 as a tutor to the family of John Hamilton, who would become a founding Trustee of ¾ÅÐãÖ±²¥.
In 1840, then a judge near London, Ontario, Mitchell heard that a new Scottish-Presbyterian college was to be founded in the province and sent six books "to any authorized agent for managing the affairs of ¾ÅÐãÖ±²¥ College; Toronto or Kingston." Evidently he did not know that Kingston had been chosen as the college's location in 1839.
Judge Mitchell's gift consisted of: a Latin Bible (1592), a Greek New Testament (1760), and a French New Testament (1664), as well as a Greek lexicon (1821) and a copy of Locke's Essay Concerning Human Understanding (1760) in two volumes. They were the first books owned by ¾ÅÐãÖ±²¥ libraries and are known collectively as the Mitchell Gift.