Taking the return tide, we passed the night in the fourth reach; very stringent orders were given to the watch to keep a sharp lookout for alligators, as a great many had been seen during the day, while we knew that on the previous night a monster of this description had attempted to get into one of the boats. We had fired at several, but with one exception had done no mischief. To be roused by the noise of the boat's keel or side grating harshly against the scaly back of an alligator, is far from being a pleasant occurrence, and on such occasions I generally found myself clutching a pistol, always kept near me, for the purpose of executing judgment upon the very first flat head that showed his nose above the gunwale. Entertaining very vivid recollections of our experience on Fitzroy River, on the first start of the boats great preparations were made against the mosquitoes; to our agreeable surprise, however, we experienced but slight annoyance from them. The exemption, however, was fully made up by the swarms of flies which infest the Adelaide, and during mealtimes availed themselves of the opportunity of popping into our mouths. There had been a fresh North-East wind the latter part of the day, which dying away was succeeded by a calm and cloudless night with a heavy dew. The thermometer was down to 77 degrees, and in the day varied from 87 to 92. RETURN OF THE BOATS. August 6. We got on board in the forenoon, when the result of our examination was heard with a satisfaction not easily expressed, but which may be readily imagined. We felt that we had discovered a river navigable for vessels of four and five hundred tons, for about fifty miles, and into fresh water, a thing hitherto unknown in Australia. We may then with justice congratulate ourselves on the importance of the discovery of the Adelaide. ADAM BAY. The bay into which it flows, named after Sir Charles Adam, is six miles deep and ten broad at the entrance, where there are 9 fathoms. The shores gradually approach each other, and at the head, where it receives the waters of the Adelaide, the width is only one mile. The mouth of the river is fronted with shoals that extend out five miles; the channel between them is narrow, 3 and 4 fathoms deep, and lies on the western side of the bay. A guide for the mouth of it is the east entrance point of the river, bearing South 40 degrees East.