Thank you very much for taking the time and effort to answer. Your information is both interesting and useful.
The Seymore Peek Headright Survey is located on the Red River, almost due north of De Kalb. (I live about five miles southwest of it.)
Mr. Peek was drowned during the tremendous flood of January 1843. His, and your great-grandmother's, ordeal was recorded in the 4 February 1843 edition of the Clarksville, Texas, newspaper The Northern Standard (page 2, column 3): "At Berlin [the Mouth of Mill Creek], a large quantity of property was lost, and a man named Peake [sic], residing two miles and a half above, was lost from a raft and drowned, as he was making his way down to the landing, for relief. His wife and a Negro man were taken from the top of a tree, after long exposure, and after she had lost the power of speech and movement. The Negro would have been exhausted in a half hour more, and unable to longer support his mistress, they would both have fallen and been swallowed up in the torrent of water. They were saved by Gen. [John H.] Dyer, who had a flat [boat], and is said to have relieved a large number of persons, taking some, from the Arkansas side, from the tops of trees."
I do not recall seeing at which school Thomas Cowan taught, but Clarksville was noted for its schools and actually had three or more at one time during the time Mr. Cowan lived there. I will be on the lookout for information concerning his teaching.
Thank you again.