Authentic letter COVER from James C. Biddle with Transcript of Letter

Authentic Letter Cover from James C. Biddle. Attached is a Transcription of the letter that once was inside this historic envelope from the American Civil War.
Headquarters, Army of the Potomac Centreville, [Virginia]
October 18th 1863
My own darling wife,
I would give so much to be with you today my own darling wife. It is Sunday and is as quiet as can be. I hear nothing of new movements of the enemy. I do not believe they will attempt to attack us here and from all I have seen, I see nothing to indicate that they have been in front of us in force. Hill's Corps or at least a portion of it followed us but I have heard nothing as to the whereabouts of Ewell or any other troops. General Sickles was here yesterday. I do not know what he was after but he returned again to Washington. He is not in fit condition to be in the field. It was with great difficulty he could move about. It would be the best thing in the world if Lee would attack us here, but I am afraid there is very little chance of it, and before long I expect we will be after him.
I would like very much to be with you for at least one week before going South again, but this is a mere conjecture of mine & may never happen. I am looking with great anxiety to events as they are passing in Tennessee. I should think before very long a great battle will be fought there and one that will tend to bring the rebellion to an end. The elections are as important as a victory in the field and it shows the South they have nothing to hope for in holding out longer - that there is nothing but men staring them in the face the longer they hold out. Starr has been ordered to rejoin his regiment. I do not think he liked it very much. He wanted to go to Washington to refit at the time they went, but now that winter is so near setting in, he would prefer being at Headquarters. I hope my dear girl the medicine Doctor M. has given you will cure you of your ailments. I wish with all my heart I could see you if it was only for a little while, but we must keep up the spirits. It will soon be impossible for either army to do anything and I then look forward to a long leave of absence. I wish I could be ordered on some duty this winter where I could have you with me. I should be then too happy for anything. Breakfast is ready.
Give my love to Ma and all & with a heart full of love for yourself, I am forever your devoted husband.