RC (DLC); at foot of text: “His Excellency The President of the United States”; endorsed by TJ as received 10 June and so recorded in SJL.

The adage NE SUTOR ULTRA CREPIDAM, sometimes translated as “cobbler, stick to your last,” admonishes against overstepping one’s expertise. Recording the anecdote in which the proverb had its origin, Pliny the Elder gave the expression as “ne supra crepidam sutor iudicaret”—criticism by a shoemaker should not go beyond the subject of shoes (Natural History, xxxv, 85).

Alexander Mackenzie returned to Canada in 1802 after spending two years in Britain, where he had been knighted in recognition of his overland expeditions from Britain’s Canadian provinces to the Arctic Ocean and the northern Pacific coast. A Philadelphia edition of the ACCOUNT OF HIS JOURNEYS had recently appeared (see John Vaughan to TJ, 8 May). The ADVANTAGES that impressed Wistar may have included Mackenzie’s affiliation with the North West Company, which enabled him to establish a base for his expeditions at Lake Athabasca west of Hudson Bay. Mackenzie also had access to French Canadian voyageurs and Indian interpreters and hunters to make up his traveling parties, as well as stocks of trade goods and some geographical information from Indian tribes. Between his two expeditions he went to England to learn the principles of navigation. Mackenzie had several years’ experience in the fur trade and described himself as “endowed by Nature with an inquisitive mind and enterprising spirit; possessing also a constitution and frame of body equal to the most arduous undertakings” and “familiar with toilsome exertions in the prosecution of mercantile pursuits.” He “not only contemplated the practicability of penetrating across the continent of America, but was confident in the qualifications” and “animated by the desire, to undertake the perilous enterprise” (DNB description begins H. C. G. Matthew and Brian Harrison, eds., Oxford Dictionary of National Biography, In Association with The British Academy, From the Earliest Times to the Year 2000, Oxford, 2004, 60 vols. description ends ; W. Kaye Lamb, ed., The Journals and Letters of Sir Alexander Mackenzie [Cambridge, 1970], 15, 18–21, 57, 58, 163, 237).

Mackenzie’s published journals included an overview of the fur trade that named several examples of the disastrous EFFECTS of smallpox on indigenous peoples in British North America. The disease “destroyed with its pestilential breath whole families and tribes” and consequently hurt the fur trade, which was Mackenzie’s source of livelihood (Alexander Mackenzie, Voyages from Montreal, on the River St. Laurence, through the Continent of North America, to the Frozen and Pacific Oceans; In the Years 1789 and 1793 [London, 1801], xiv, xvii, liii, lvii, lxxvii, lxxviii, lxxxii, cxvii; DNB description begins H. C. G. Matthew and Brian Harrison, eds., Oxford Dictionary of National Biography, In Association with The British Academy, From the Earliest Times to the Year 2000, Oxford, 2004, 60 vols. description ends ).

TJ and Wistar, who had both studied the megalonyx fossils from Virginia in 1797, were interested in similarities and differences between the megalonyx and the skeleton of the MEGATHERIUM that had been excavated in South America and mounted in Madrid. Charles Willson Peale acquired illustrations of the megatherium bones from Philippe Rose Roume, a former French commissioner to Saint-Domingue who was in the United States for several months in 1801–2. Roume first obtained pictures of the fossils in Spain in 1795. Peale put the illustrations on display in his museum in Philadelphia, in the same room as the mastodon skeleton from New York State (Philadelphia Gazette, 10 Mch. 1802; APS, Transactions, 4 [1799], 526–31; Robert Hoffstetter, “Les rôles respectifs de Brú, Cuvier et Garriga dans les premières études concernant Megatherium,” Bulletin du Muséum National d’Histoire Naturelle, 2d ser., 31 [1959], 538–9; Laurent Dubois, Avengers of the New World: The Story of the Haitian Revolution [Cambridge, Mass., 2004], 196, 226; Peale, Papers description begins Lillian B. Miller and others, eds., The Selected Papers of Charles Willson Peale and His Family, New Haven, 1983–2000, 5 vols. in 6 description ends , v. 2, pt. 1:381–6, 440, 443n; Madison, Papers description begins William T. Hutchinson, Robert A. Rutland, J. C. A. Stagg, and others, eds., The Papers of James Madison, Chicago and Charlottesville, 1962–, 32 vols. Sec. of State Ser., 1986–, 8 vols. Pres. Ser., 1984–, 6 vols. Ret. Ser., 2009–, 1 vol. description ends , Sec. of State Ser., 2:74, 94; Vol. 29:298–9, 300n; Benjamin Smith Barton to TJ, 9 Feb. 1802).

BONES OF THE HEAD OF THE MAMMOTH: that is, the partial skull that John Brown of Boone County, Kentucky, sent to Peale; see Brown’s letter to TJ of 28 Apr. and Peale’s of 6 June. For the arrival of the fossil in Philadelphia, see Peale’s letter of 10 June.

The mastodon skeleton that Peale exhibited in Philadelphia lacked the upper part of the skull, so Peale drew on the anatomy of the ELEPHANT to create replicas of the missing bones (Peale to TJ, 21 Jan. 1802).