At eight o'clock on the morning of the 15th of May, the three steamers weighed anchor, and stood up Pearl river, the Westfield and the Clifton following in the wake of the Sachem. At eleven o'clock, Pearlington was reached, a straggling village. Here two schooners and a small steamer (the William Hancock) were found, and boarded by Mr. Harris of the Sachem; but when it was proved that they had not been engaged in aiding the rebel cause, they were not further molested. The steamers of the mortar flotilla ascended the river about thirteen miles above Pearlington, when the stream became quite narrow, and the turns so abrupt, that further progress for the larger boats seemed to be impracticable. Captains Renshaw and Baldwin therefore anchored their vessels, and went on board of the Sachem, which, on account of her lighter draught and less beam, could ascend higher, and was besides easier to manage. While pushing on with her, it was frequently necessary to fasten her stern to the trees, and to tow her bow around at the very abrupt turns in the river. Within three miles of Gainesville, where the stream became extremely narrow and crooked, with the shores on both sides thickly wooded, the Sachem encountered a very sudden ambuscade, and received a heavy fire of musketry from the eastern bank. This was immediately returned from the vessel by some sixty rifle and musket shots, and discharges of small arms were continued in rapid succession from both sides for some time. The executive officer of the Sachem, Mr. J. G. Oltmanns, of the United States Coast Survey, while on the forecastle directing the crew, was dangerously wounded by a rifle ball in the breast, and fell. He was at once removed to the cabin, and Acting Assistant Harris directed to take his place. This he did instantly, and remained in that position during the whole of the subsequent cruise. As soon as the long guns of the Sachem and the Parrott rifle 20-pounder could be brought to bear, the thicket was cleared by discharges of canister and grape, and the fire of the enemy was silenced. No other casualties occurred on board of the steamer, but many of the crew narrowly escaped harm, particularly those who were near the wheel house. The sailing master and the steersman had their clothes pierced by bullets, and the sides and decks of the steamer were similarly marked in many places. The river, becoming still narrower and more crooked above Gainesville, it was found entirely impossible to force the Sachem higher up. Captain Renshaw therefore directed her to be turned down stream. In this manoeuvre, much difficulty was encountered. It succeeded only by cutting the overhanging trees on shore, then backing her into the bank, fastening her stern, and towing her bow around with the boats. While turning thus, one of the Sachem's boats and the Clifton's gig were smashed in the floating logs, and the flagstaff was carried away by hanging branches of the forest. The national ensign, however, was set on