From 7 to 9, aboard the United States school-ship Minnesota, lying up the North river. Captain Luce sent his gig for us about sundown, to the foot of Twenty-third street, and receiv'd us aboard with officer-like hospitality and sailor heartiness. There are several hundred youths on the Minnesota to be train'd for efficiently manning the government navy. I like the idea much; and, so far as I have seen to-night, I like the way it is carried out on this huge vessel. Below, on the gun-deck, were gather'd nearly a hundred of the boys, to give us some of their singing exercises, with a melodeon accompaniment, play'd by one of their number. They sang with a will. The best part, however, was the sight of the young fellows themselves. I went over among them before the singing began, and talk'd a few minutes informally. They are from all the States; I asked for the Southerners, but could only find one, a lad from Baltimore. In age, apparently, they range from about fourteen years to nineteen or twenty. They are all of American birth, and have to pass a rigid medical examination; well-grown youths, good flesh, bright eyes, looking straight at you, healthy, intelligent, not a slouch among them, nor a menial--in every one the promise of a man. I have been to many public aggregations of young and old, and of schools and colleges, in my day, but I confess I have never been so near satisfied, so comforted, (both from the fact of the school itself, and the splendid proof of our country, our composite race, and the sample-promises of its good average capacities, its future,) as in the collection from all parts of the United States on this navy training ship. ("Are there going to be _any men_ there?" was the dry and pregnant reply of Emerson to one who had been crowding him with the rich material statistics and possibilities of some western or Pacific region.) _May 26_.--Aboard the Minnesota again. Lieut. Murphy kindly came for me in his boat. Enjoy'd specially those brief trips to and fro--the sailors, tann'd, strong, so bright and able-looking, pulling their oars in long side-swing, man-of-war style, as they row'd me across. I saw the boys in companies drilling with small arms; had a talk with Chaplain Rawson. At 11 o'clock all of us gathered to breakfast around a long table in the great ward room--I among the rest--a genial, plentiful, hospitable affair every way--plenty to eat, and of the best; became acquainted with several new officers. This second visit, with its observations, talks, (two or three at random with the boys,) confirm'd my first impressions. MATURE SUMMER DAYS AND NIGHTS