A mile or two below Charleroi is Lock No. 4, the first of the quartet of obstructions between Brownsville and Pittsburg. We are encamped a mile below the dam, in a cozy little willowed nook; a rod behind our ample tent rises the face of an alluvial terrace, occupied by a grain-field, running back for an hundred yards to the hills, at the base of which is a railway track. Across the river, here some two hundred and fifty yards wide, the dark, rocky bluffs, slashed with numerous ravines, ascend sharply from the flood; at the quarried base, a wagon road and the customary railway; and upon the stony beach, two or three rough shelter-tents, housing the Black Diamond Brass Band, of Monongahela City, out on a week's picnic to while away the period of the strike. It was seven o'clock when we struck camp, and our frugal repast was finished by lantern-light. The sun sets early in this narrow trough through the foothills of the Laurel range. * * * * * McKeesport, Pa., Saturday, May 5th.--Out there on the beach, near Charleroi, with the sail for an awning, Pilgrim had been converted into a boudoir for the Doctor, who, snuggled in his sleeping-bag, emitted an occasional snore--echoes from the Land of Nod. W---- and our Boy of ten summers, on their canvas folding-cots, were peacefully oblivious of the noises of the night, and needed the kiss of dawn to rouse them. But for me, always a light sleeper, and as yet unused to our airy bedroom, the crickets chirruped through the long watches. Two or three freighters passed in the night, with monotonous swish-swish and swelling wake. It arouses something akin to awe, this passage of a steamer's wake upon the beach, a dozen feet from the door of one's tent. First, the water is sucked down, leaving for a moment a wet streak of sand or gravel, a dozen feet in width; in quick succession come heavy, booming waves, running at an acute angle with the shore, breaking at once into angry foam, and wasting themselves far up on the strand, for a few moments making bedlam with any driftwood which chances to have made lodgment there. When suddenly awakened by this boisterous turmoil, the first thought is that a dam has broken and a flood is at hand; but, by the time you rise upon your elbow, the scurrying uproar lessens, and gradually dies away along a more distant shore. We were slow in getting off this morning. But the dense fog had been loath to lift; and at first the stove smoked badly, until we discovered and removed the source of trouble. This stove is an ingenious contrivance of the Doctor's--a box of sheet-iron, of slight weight, so arranged as to be folded into an incredibly small space; a vast improvement for cooking purposes over an open camp-fire, which Pilgrim's crew know, from long experience in far distant fields, to be a vexation to eyes and soul.