The southern arm of the Adelaide River, and about fifteen miles near the mouth of the other branch, still remaining to be explored, I started on this interesting service the day of the return of Captain Wickham, August 4th. We soon found that the one we ascended promised nothing, from there being no tidal stream of any consequence; still we hoped to trace its rejunction with the main branch, but after proceeding in a general South by West direction five miles, and East-South-East the same distance, it became so narrow that the mangroves on each side entirely blocked up the passage, and stopped the boat's progress. I here again felt the inconvenience of our not being furnished with one of the pendulum horizons, invented by Captain Becher, R.N.* It being high-water, and as the shore was lined with an impenetrable growth of mangroves, we were unable to land. In vain did I try, by cutting down some of them, to find a rest for the artificial horizon on one of the stumps; they were so connected with each other beneath the water, by a perfect network of roots, that although several of the surrounding trees were felled, a tremulous motion was still conveyed from a distance, and I consequently lost the observation for latitude. (*Footnote. I strongly recommend this ingenious invention to every seaman. In foggy weather it will save hours of anxiety, and may often prevent the horrors of shipwreck.) The saltwater arm of the Adelaide we found had another branch, which took us eight miles in a South-West direction, terminating like the other, and at low-water being a mere ditch. There was nothing picturesque in following the windings of these creeks or inlets; a tall growth of mangroves with their stems immersed, rendering the view limited and wearisome. We, however, were urged on by hope, being in momentary expectation that each turn would bring some change, while to add to the zest of our proceedings we felt ourselves to be the first Europeans who had traversed these parts. Now and then the deep stillness of nature would be broken by the mournful cry of a curlew, disturbed by the splash of the oars, while sometimes a heavy flapping of wings was heard amid the mangroves, and out would start suddenly three or four white ibises with black necks, giving utterance to a peculiar cry, which faintly resembles that of the male guinea fowl. All else was deep unbroken silence. By evening we had again reached the entrance of the river, where we passed the night, during which there was a very heavy dew. August 5.