Note III-9 — Chapter III · ITINERARY, CONCLUDED: LEECH LAKE TO ST. LOUIS, FEBRUARY 1ST-APRIL 30TH, 1806.

David Thompson, the great explorer and surveyor, b. St. John's parish, Westminster, Eng., Apr. 30th, 1770, d. Longueuil, opposite Montreal, Canada, Feb. 16th, 1857, and now with his wife in Mt. Royal cemetery. His activities compassed half a century, say 1790-1840, during some of which years he seems to have been almost ubiquitous—so extensive were his travels, in the service of the H. B. Co., N. W. Co., and on professional duties in connection with the survey of the boundary between the British possessions and the United States. Mr. Thompson was a good practical astronomer and an admirable geographer. Some of his determinations would not easily be surpassed in accuracy by the best modern methods. He was also an assiduous journalist, and a good draughtsman; but most of his work has never seen the light. The manuscripts which he left are believed to cover the long period of years during which he traveled and observed; and to include not only his personal narrative, but also the mathematical tables by which his astronomical observations were worked out for the determination of latitude and longitude. They have more than once been drawn upon for historical and geographical data; but no publication of such a thorough digest of Thompson's life and work as could have been prepared from these materials under competent and critical editorship has ever been made. A brief recital of his journeys was read by J. B. Tyrrell, B. A., etc., before the Canadian Institute, Mar. 3d, 1888, and published that year, Toronto, 8vo., pp. 28. The official records I have mentioned must not be confounded with certain fragments of Thompson's MSS., now the property of a Mr. Charles Lindsey of Toronto, and recently offered for sale. These are about 600 foolscap pp. in Thompson's handwriting, drawn up very late in life—being thus by no means his original journals and field note-books. Thompson was on the Missouri at the Mandan villages Dec. 29th, 1797-Jan. 10th, 1798—thus before Lewis and Clark, Oct. 27th, 1804-Apr. 7th, 1805, and the younger Alexander Henry, July and Aug., 1806. While here he undertook to determine from Indian information the source of the Yellowstone r., and made one of the most extraordinary computations on record; for his figures agree within 20 m. or less with the true latitude and longitude. Thompson was the first white man who ever descended the Columbia r. from its head-waters to the point where Lewis and Clark struck it, Oct. 16th, 1806; this voyage was made in the summer of 1811, and protracted to the Pacific at Astoria. That journey to which Pike refers was made in 1798. Thompson came down the Turtle River route to Cass l., late in April, and stopped at John Sayers' house, located by him in lat. 47° 27´ 56´´ N. and long. 95° W. If we marvel why such a man as Thompson missed the honor of discovering the source of the Mississippi, when that prize was so near at hand, we may remember that the Turtle River head-waters were already the accepted source, as being the furthest N. Leaving Cass l. May 3d, Thompson descended the Mississippi through Lake Winnibigoshish, and so on to the N. W. Co. house at Sandy l.; thence he went up Prairie or Savanna r., the usual traders' route, portaged over to waters of the St. Louis, and descended this river to the Fond du Lac house, which stood 2½ m. from Lake Superior. This journey was from the post on the Assiniboine r., at the mouth of Souris or Mouse r., which he left Feb. 25th; he reached Fond du Lac May 10th, or in 2 months and 18 days.