The Macquarie, although it at length ceased to run, kept up the appearance of a river to the very marshes; but the bed of the Castlereagh might have been crossed in many places without being noticed, nor did its channel contain so much water as was to be found on the neighbouring plains.
There are two circumstances upon which the magnitude, and velocity of a river, more immediately depend.

The first is the abundance of its sources, the other the dip of its bed.

If a stream has constant fountains at its head, and numerous tributaries joining it in its course, and flows withal through a country of gradual descent, such a stream will never fail; but if the supplies do not exceed the evaporation and absorption, to which every river is subject, if a river dependant on its head alone, falls rapidly into a level country, without receiving a single addition to its waters to assist the first impulse acquired in their descent, it must necessarily cease to flow at one point or other.

Such is the case with the Lachlan, the Macquarie, the Castlereagh, and the Darling.

Whence the latter originates, still remains to be ascertained; but most undoubtedly its sources have been influenced by the same drought that has exhausted the fountains of the three first mentioned streams.
In supporting his opinion of the probable discharge of the interior waters of Australia upon its north-west coast, Mr.Cunningham thus remarks in the publication from which I have already made an extract.
"To those remarkable parts of the north-west coast above referred to in the parallel of 16 degrees south, the Macquarie river, which rises in lat.