They are inferior in size to the common European wild duck, but are marked in much the same manner on the breast.  The back is a dark brown, while the wings, still darker, are slightly bronzed at the tips.  Their singularly long legs are of a pale flesh colour, while the web on the foot is very much arched near the toes, giving greater pliability to the foot and a power of grasping, which enables them to perch on trees.  The head and bill, the latter of a pale ash colour, are both large.  When on the wing they make a peculiar though pleasing whistling sound, that can be heard at a great distance,* and which changes as they alight, into a sort of chatter.  Their perching on trees is performed in a very clumsy manner, swinging and pitching to and fro.  We subsequently often found them on the rivers on the North coast, but not within some miles of their mouths or near their upper waters, from which it would appear that they inhabit certain reaches of the rivers only:  we never found them in swamps.  The farthest south they were afterwards met with, was on the Albert River in the Gulf of Carpentaria, in latitude 18 degrees South, which gives them a range of six and a half degrees of latitude over the northern part of the continent.  Their nests never came under our notice, and consequently we are not aware either of the size or colour of their eggs; neither did we see any young birds during the period of our observation, ranging from July to November only.**

(Footnote.  Mr. Eyre has since informed me that there is a whistling-duck, something similar, on the Murray River, but is not aware that it has the peculiar habit of perching on trees.)

(**Footnote.  Mr. Gould, who had previously described this bird (Leptotarais Eytoni) being desirous of figuring it in his splendid work, has been furnished with this account.)

EXPLORATION OF THE SOUTHERN BRANCH OF THE ADELAIDE.

August 4.

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.