From Capt. Van Doorn's Company.

Cumberland Gap, June 23d.

Mr. Editor. -- Dear Sir: Through a kind providence, the 16th has been permitted to encamp unharmed in the land of Dixie. We have been since the eve of the 18th in possession of that long-wished-for place, the Gap. It is certainly one of the strongest natural positions in America. When we consider that it is ours without the loss of one of our comrades, it speaks much in favor of our worthy Commander. And is but another proof of the skill and generalship of those who love and fight for the Union. In hunting for the last ditch, they left behind them 5 large cannon, their tents and a great amount of soldier plunder, all of which can do us no good, but it will be a great and irreparable loss to them.

The fortifications show that military men have been at work, leaving nothing undone which was in their power to do, to insure success. Their works consist of strongly built forts for cannon, occupying such positions as to command every approach besides those, there are variously estimated from 3 to 5 miles of rifle pits, for the most part strongly constructed and well engineered. While it is true that we possess this Gibraltar without hard fighting, it is equally true that it detracts nothing from the glory of the achievement, in that, it has been made without the shedding of blood. Could you with our friends, have gazed upon our columns as they step by step ascended the Pine and Cumberland mountains -- ah! yes, could you have experienced the fatigue of this latter day ascension, you would know that what was not done by hard fighting was done by hard marching. If a living picture of our march could be drawn, giving in detail the difficulties overcome, it would be hung up in the parlor of every man in this Division who lives to return. Dead mules, broken wagons, overcoats and blankets mark the path of that part of the Division going through Big Creek Gap; and I am told that those who came through Wilson's Gap, fared, if possible, even worse. Yet we feel perfectly satisfied with our reward - a good conscience and possession of the Gap. On the eve of the 18th, (long will it be remembered, ) the 16th was led into the fortifications. A national salute by Capt. Foster's Battery and three times three by given for the Flag of the Union, which now floats so beautifully from the ramparts where so short a time before the Stars and Bars waved defiance to it. I hope, yes, I believe, that if permitted to advance, it will kiss the breeze from the dome of Lury Hall in Knoxville before ten days.

Only having a few moments to write before mail, I must close by saying to those having friends in Company K, that their health and spirits were never better.

Yours truly, J. LAMM.