With respect to the construction of the chart prefixed to this Journal, it is thought proper to observe, that the situation of the principal stations of Bathurst, and the depot on the Lachlan River, were ascertained by celestial observations, and connected by a series of triangles, commencing at the latter point, and closing at Bathurst. New base lines were frequently measured, and any unavoidable errors which might arise from the nature of the country were corrected at every proper opportunity by observed latitudes; so that on the return of the expedition to Bathurst, I had the satisfaction to find the connection of the angles complete, the error in the whole survey not exceeding a mile of longitude. The instruments chiefly used were a small theodolite by Ramsden, and Kater's pocket compass [Note: A most valuable instrument, combining all the advantages of the circumferentor, without being so liable to be damaged and put out of order by carriage.], with the addition of an excellent sextant, pocket chronometer, and artificial horizon. I have to lament that our mountain barometers were broken at an early stage of the expedition; the height however of some principal points had been previously obtained, and is marked on the chart; these in two instances were verified by geometrical measurement, and the difference was found to be too trilling to be noticed. The conveyance of such delicate instruments is always attended with great risk, and in our case peculiarly so, our means being only those of horseback. I am afraid that a method of constructing those instruments, so as to place them beyond the reach of injury by carriage, will always remain among the desiderata of science. I have given to our thermometrical observations the form of a chart, as affording the readiest view of the atmospherical changes which took place during our journey. The winds and weather are also more particularly noticed on the same sheet than in the narrative. It may perhaps be not superfluous to mention, that it is the intention of His Majesty's Government to follow the course of the Macquarie River, and it is sanguinely expected that the result of the contemplated expedition will be such as to leave no longer in doubt the true character of the country comprising the interior of this vast island. It would be as presumptuous as useless to speculate on the probable termination of the Macquarie River, when a few months will (it is to be hoped) decide the long disputed point, whether Australia, with a surface nearly as extensive as Europe, is, from its geological formation, destitute of rivers, either terminating in interior seas, or having their estuaries on the coast. J. O. Sydney, New South Wales, Dec. 11, 1817. ERRATA: 12 items of errata, listed in the book at this point, have been corrected in this eBook. JOURNAL OF AN EXPEDITION IN AUSTRALIA--Part I