No more striking testimonial could be asked than the constant applications from men of mature life for the books that so charmed them as boys, in order that their own sons may have the same enjoyment. Or, could anything be more conclusive than that one of the most prominent men in the public life of our state still turns to his favorite "Oliver Optic" books for pleasurable relief when the cares of the day have made rest seem almost an impossibility? Critics come and critics go, but the hold of "Oliver Optic" upon the popular mind remains unchanged. No mean-souled man could so endure. As he said himself: "I have never written a story which could excite the love, admiration, and sympathy of the reader for an evil-minded person or bad character. This has been my standard; and, however others may regard it, I still deem it a safe one." All who had any connection with the publication of Mr. Adams's works loved the man, and his visits were marked with cheerful words for each one, in whatever capacity employed, and will linger helpfully while life remains. All who knew him join in honoring the unfailing kindness and clean, true nature of this great writer and noble friend of youth. LEE AND SHEPARD. APRIL 1, 1899. PREFACE "AN UNDIVIDED UNION" is the sixth and last volume of the "Blue and Gray--On Land" series. Like its predecessors it relates the adventures of the Riverlawn Cavalry, a Union regiment, raised in Kentucky, and participating in the daring campaigns undertaken by the Army of the Cumberland. The fifth volume of the series left the regiment at Murfreesboro, after most gallant service performed at the battle of Stone River; in the present book is given an account of the operations around Murfreesboro, before Tullahoma, and through the bloody battles of Chickamauga, Chattanooga, Lookout Mountain, Missionary Ridge, and other contests leading up to Sherman's famous March to the Sea. As in the other stories of this series, Deck Lyon has again come to the front as a daring hero, but his achievements are closely seconded by his foster brother, Artie, and by the firm friend of the two, Captain Life Knox. If Deck does some smart things, it must be remembered that he was a smart young man or he would not have risen to be senior major, first battalion, of the Riverlawns. Besides this, the major still had with him his famous charger, Ceph, a steed with almost human intelligence on certain points, and one that had helped him to escape from many a perilous position.