FROM its vast size and its peculiar conditions of physical geography the island-continent of Australia presents formidable difficulties alike to the topographical and the geological surveyor. Of its wide desert interior we know nothing more than what has been seen or conjectured along the tracks of the few adventurous men who have penetrated it. The eastern and southern colonies have been more or less thoroughly geologised, and expeditions have been sent to make known the capabilities of portions of the western and northern coasts. Several of the colonies have equipped geological surveys, though they have not always cared to maintain them. A great deal of miscellaneous knowledge regarding the rocks of the country has thus been acquired, but it is scattered through hundreds of blue-books, reports, memoirs, transactions of societies, newspapers, and other publications. Those who are most familiar with Australian geology, can best judge whether the time has now come when this store of diffused information may be profitably condensed in the form of a general map of the whole country. Mr. Brough Smyth has deemed that it may, and accordingly he has produced the present map—the first general geological map of Australia which, so far as we are aware, has been published.