Though the War Department at Washington hes-itates, as the telegraph informs us, to receive as authentic the news of the destruction of a part of the Utah army provision trains by the Mormons, there remains no longer any room for doubt upon the subject. We publish to-day a letter from our special Utah correspondent, containing the full par-ticulars, and no doubt by this time the War De-partment is in possession of dispatches on the same subject, forwarded by Col. Smith, by tbe same ex-press which brought our letter. We also print au extract from The Leavenworth Times containing some particulars of tbe attack, as forwarded by ex-press to Eussell & Waddell of that city, the con-tractors to whom the wagons belonged. The date of the attack was the 5th of October, about mid-night, and the place that part of the road inter-vening between the Big Sandy and the Green River, about half way from the South Pass to Fort Bridger. The whole distance between these two points is about a hundred and thirty miles, near fifty of which, in the neighborhood of the Big Sandy, is a complete desert.
At the time of the attack, the van of the expedi-tion under Col. Alexander, now the Commander-in-Chief, which was marching upon Fort Bridger, was encamped on Ham's Fork, about thirty miles in advance, while the rear of the expedition under Col. Smith had not yet reached the South Pass. The number of wagons destroyed is stated at seven-ty-five or seventy-eight, all of which were burnt with their contents except five, which were given up to the teamsters with sufficient rations to ena-ble them to reach Fort Laramie. No personal in-jury was offered to any one, the assailants disclaim-ing any intention to shed blood unless some of the Saints should first be killed. As to the number of the assailants and their backers, we have no very definite information. The attack was made by two distinct parties, one of the trains be-fog some miles behind the other two. Neither of these parties, according to the information obtained by our correspondent, exceeded a hundred men. The suggestion that Heber C. Kimball was with them is not probable, as he is doubtless better at preaching than at fighting. The particulars of the attack were, however, imperfectly known in Col. Smith's camp, whence our letter was written. A messenger had arrived who had been the bearer of dispatches from Col. Alexander to Col. Smith, but, as he had fallen into the hands of the Mormons on the way, he had obeyed his orders by destroying his dispatches. What was known in Col. Smith's camp appears to have been derived from the verbal statements of this messenger, and from a circular letter dispatched by Capt. Marcy to the trains on the road, advising them to place themselves under Col. Smith's protection.
The entire force of fighting men in the expedition does not probably exceed ten or eleven hundred. It includes the entire Tenth Regiment of Infantry, eight companies of the Fifth Infantry, a detachment of the Fourth Artillery, with six light pieces, and about sixty men, and an ordnance train with heavy pieces, of about the same strength. The teamsters and other laborers attached to the expedition might swell the entire force to sixteen hundred or more, but these last would have their hands fall in taking care of their cattle. From the South Pass to Fort Bridger is, as we have stated, a hundred and thirty-one miles, of which more than a third part is a per-fect desert, and the whole a difficult country, with very little grass. What little there is, the same parties of Mormons employed in intercepting the trains will doubtless set on fire and destroy.
From Fort Bridger to Salt Lake City, the direct road across the mountains is one hundred and thir-teen miles, but this is a very difficult route, with many narrow passes, liable to be blocked with snow, hardly practicable so late in the season at any rate, and still less so with the prospect of active resistance on the part of the Mormons. There is another road, following the valley of the Bear river north to Soda Springs, where the Ore-gon road forks off, and then turning south by the game valley and the eastern shore of the Great Salt Lake. This route nearly doubles the distance, but it is much more practicable, and, should the Expe-dition advance into the valley, it will probably be by this road. The great difficulty in the advance is the subsistence of the cattle of the provision trains.
It must be confessed that the dilatoriness of the War Department in not starting the expedition sea-sonably on its march, and the detention of the troops in Kansas, have placed both the Government and the expedition in a very awkward predicament. Every motive, whether of policy, of humanity or self respect, required that, if military possession were to be taken of the Mormon Valley, it should be done under circumstances and with a force to overcome every idea of resistance. To be obliged to retire before the Mormons would be mortifying enough; to have Salt Lake Valley tamed into the scene of a desperate and deadly struggle would be still worse.
The whole difficulty has originated from the use-less and foolish detention of the troops in Kansas. Instead of marching seasonably forward on the ex-pedition for which they were intended, they were long kept in that Territory for the sake of prevent-ing the people of Lawrence from organizing a Mu-nicipal Government. During this delay, they suf-fered greatly by desertion. Some of the troops destined for this service still remain behind, and the expedition has thus been reduced to about half the force originally intended. Under these circum-stances, whatever the result may be—and there seems little ground to anticipate any but an unpleas-ant one—the responsibility will be at the door of those who kept the troops in Kansas when they should have been marching on Utah.
