This morning the thermometer was down to 72 degrees at daylight, which gave us the novel sensation of cold. It was late in the forenoon before the violent ripplings at Tide-Race Point had subsided sufficiently to allow of our passing it. The rate of the current at this point appeared at times scarcely less than eight knots per hour, and traversing a rocky ledge, extending to some islands, and nearly dry at low-water, rendered it almost impassable, except when nearly high tide. CASCADE BAY. In the afternoon we reached the cascade discovered on our way to the northward, and from which the bay within which it is received its name. We spent an hour or two luxuriating in the thorough enjoyment of a treat so rare, as this beautiful stream must be considered in North-western Australia. In the evening we continued our return to Port Usborne, by a channel leading from the bottom of Cascade Bay into the large sheet of water first seen from Compass Hill; our progress was arrested at its inner entrance by the violence with which the tide rushed through, and we were therefore obliged to pass another night in the boats. RETURN OF THE BOATS. March 29. We reached the ship this morning, entering Port Usborne by a narrow rocky channel, on its North-West shore; on the precipitous sides in this passage we noticed several of the Rock Kangaroo. We found that Mr. Usborne had returned three days before us: from his account of the islands he had visited, they appear to have the same sterile character as most of those we had seen; in other respects, his trip was void of interest, beyond that of surveying. During the absence of the boats, tidal and magnetic observations had been made, some specimens in Natural History had been collected, and all that could in any way add to the interest of the expedition, had been as well attended to as the means placed at our disposal would allow. We closed at Port Usborne our explorations in King's Sound, the result of which enabled us to fill up the gap long existing in the charts of the North-west coast of Australia, and which had for years been the theme of much ingenious geographical speculation. The result of our labours, if it had been less brilliant than eager anticipation at the onset led us to hope for, had nevertheless been on the whole satisfactory. The river Fitzroy, although not of the magnitude that we hoped to find, was still an undoubtedly valuable acquisition to our stock of geographical knowledge, and offered a way of access into the interior, of which we had availed ourselves to the extent of 90 miles, and which subsequent explorers might yet further improve: while in many minor yet important matters, much had been done, and much seen, to more than compensate for the disappointments and annoyances inseparable from the pursuits of the adventurer. LEAVING PORT USBORNE. March 30.