as to be easily destroyed by such slight changes as are effected by long-continued rains, great floods, or the alteration of the course of a stream. The ashes and charcoal of their cooking-places, too, would in time be removed, little by little, in seasons of drought, when hot winds prevailed. The light material, dried by the sun, would be blown away. It would not be safe therefore to assume, because no remains of these ovens and stone-circles have been found in post-Pliocene deposits, that they did not once exist. The period of the first occupation of the continent by the Australian race must be determined by other than such negative evidence as this. It must be ascertained by the position in the soil of less perishable monuments. Their stone implements, almost indestructible in their character, are surer guides, in considering this question, than any other of their works of art; and the inferences to be derived from the position of these in recent accumulations is discussed elsewhere. Yet it is not without instruction, when we view the size and position of the mounds and circles, to reflect on the immense periods of time which must have elapsed since some of these were first visited by the natives. The thought of most persons on seeing a very large mound is that the population has been in past times very dense; but this theory is untenable. The country has always been sparsely peopled—the food supplies and the modes of procuring food regulated the numbers; and the great size of the mounds is due to the frequent visits of a few persons during long periods, and not to any sudden accumulation caused by the presence of a multitude. This fact is borne out by the formation of the mounds. The layers of which they are composed point clearly to the slow and gradual heaping-up of small quantities of material from time to time.
The sites for Mirrn-yong heaps appear to have been chosen generally in localities near water; and whether because the site was the most convenient that could be chosen, or that it was always preferred because blacks had frequented it previously, is not known; but it is well ascertained that each site was used as a cooking-place by generation after generation. They are often found near or slightly within the margin of a forest or a belt of timber; and the situation is nearly always well sheltered.
There are numerous old Mirrn-yong heaps on the banks of the River Plenty, on the Darebin Creek, and the Merri Creek, near Melbourne; they are seen in all parts of the Murray basin, and on the coast; and there are large heaps in the Western district, some of which I have examined.
They are in general of an oval shape, about one hundred feet in length and about forty feet in breadth, and rising to a height of twelve feet or more. They are composed of burnt clay, a little soil, quantities of charcoal and ashes, burnt and unburnt bones, and stones. They enclose numerous fragments of black basalt, chips of greenstone, in some places whole and broken tomahawks, and in more than one have been found human skeletons, as if they had been used in later times as places of burial.
The late Mr. D'Oyly Aplin, at one time Acting Director of the Geological Survey of Victoria, and for a long period a Geological Surveyor, was very active in making researches in reference to these Mirrn-yong heaps; and he obtained much interesting information respecting a group of mounds on Mr. John L.
