DEAR SIR: I inclose you herewith, on another page, the results of my father's observations of latitude and longitude, so far as I have been able to collect them. His calculations indicate great pains and labor to obtain accurate results. They are too voluminous to copy. I trust, however, that I have been as particular as was necessary in the inclosed memoranda. If anything else is wanting, I should like you to inform me. I am, sir, with great respect, Your obedient servant, MALCOLM DOUGLASS. V. _Results of Observations for Latitude and Longitude during the Expedition of 1820._ By DAVID B. DOUGLASS, Capt. Engineers, U.S.A. {By 3 sets of observations at Cunningham's } { Island, 1819, and reduced by } { exact measurement on the Boundary } { Bay } { } Mean {By 1 set of observations at Gibraltar } latitude { Island (Put-in Bay), taken, like the } of { preceding, in 1819, and reduced as } 42° 19´ 20´´ Detroit { before } { } {By 1 set of observations taken on } { Sugar Island, and reduced as before } { } {By mean results of 2 sets of observations--May} 17 and 21, 1820 } {By mean observation, Sept. 29, 1820 } Mean longitude of Detroit, by 6 sets of observations, May 17 and 19, 1820 82 39 00 Latitude of Presque Isle, Lake Huron, June 5, 1820 45 19 45 Latitude of Mackinaw, by 4 sets of observations, June 7 and 11, 1820, by meridian observations, Sept. 12, 1820 45 50 54 Height of Fort Holmes. From the water to the brow of the hill near Robinson's Folly, nearly on a level with Fort Mackinaw 115.8 Thence to the top of the block H of Fort Holmes 260.9 ----- Total height, 376.7 feet Longitude of Mackinaw, by several sets of observations, Sept. 12, 1820 84 28 40 Mean latitude of Sault de St. Marie, June 16, 1820 46 26 45 Latitude of Turtle Camp, on Lake Superior, June 22--primitive bluff (Granite Point.--S.) 46 41 15 Latitude of Keweena Camp 47 02 30 Mean latitude of Sandy River, July 4, 1820 46 55 24 Mean longitude (by 25 observations for degrees, and 25 observations for time). In time, 6 h. 3 m. 48 sec. In degrees 90 57 00