It should be added that the river invariably opens for navigation the first week in May. This year the spring was early--bluebirds and robins on the 8th of April, geese on the 12th, with poplars in bud. Discovery and Exploration of the Yukon (Pelly) River By ROBERT CAMPBELL, F.R.G.S. (_Former H.B.C. Chief Factor_) _NOTE--Sir George Simpson expressed his satisfaction regarding these explorations in a letter to Mr. Campbell, the author, and spoke of the arrangement made by H.B.C. with Russia for a great stretch of Alaskan territory. The letter follows:_ Red River Settlement, 16th June, 1839. To R. Campbell, Esq., Fort Halkett. Dear Sir: I have much pleasure in acknowledging receipt of your letter of 17th September, and have to express my entire satisfaction with your management in the recent voyage down the Pelly or Stickine river, bearing ample evidence that the confidence reposed in you was well placed. I was always of the opinion that the Pelly and Stickine rivers were identical, but many of my friends in this country thought differently. You have at length, however, set the question at rest, and your writing the note to our gentlemen on the coast was very judicious. I last winter concluded an arrangement for the Company with Baron Wrangle, acting on behalf of the Russian-American Company, by which we become possessed of the whole of the Russian mainland territory (for a term of ten years) up to Cape Spencer. By that means we become possessed of their establishment situated on Point Highfield, entrance of Stickine river, immediately, and have access to the interior country through all the rivers falling into the Pacific to the southward of Cape Spencer. This arrangement renders it unnecessary for us now to extend our operations from the east side of the mountains or Mackenzie river, as we can settle that country from the Pacific with greater facility and at less expense. Your services will now therefore be required to push our discoveries in the country situated on the Peel and Colville rivers and I am quite sure you will distinguish yourself as much in that quarter as you have latterly done on the west side of the mountains. With best wishes, believe me, Very truly yours, (Signed) GEORGE SIMPSON. The Yukon is the largest river that flows from the American continent into the Pacific ocean. Rising as the Pelly in the Rocky Mountains on the northern frontier of British Columbia, it maintains a westerly direction for several hundred miles. It crosses the 141st meridian, which forms the eastern boundary of Alaska, and holding a northwest course for more than six hundred miles, it is joined by the Porcupine river from the north. Up to this point it is called the Pelly, but for the remaining 1200 miles of its course to its embouchure in Behring Sea it is known as the Yukon.