LITTLE more than a glance at the records of mining in Victoria is sufficient to convince that the enormous quantity of gold produced has, either directly or indirectly, been derived almost wholly from lodes in rocks of Silurian or earlier age; all the more recent geological formations having, as far as they have been tested, proved to be comparatively barren. It is a matter of common knowledge, however, that in other parts of the world payable auriferous lodes are found in rocks of all geological ages. Their general occurrence in Silurian strata is of course well known; in Nova Scotia they are found in Lower Carboniferous conglomerates; in California in rocks of Jurassic age, while the auriferous quartz veins of Viiriispatak, in Transyllvania, traverse Tertiary sandstones:, Indeed, evidence is not wanting from many parts of the world that metalliferous deposits are in progress even at the present day. J. A. Phillips remarks) that "Many other localites where quartz veins almost identical in their general features with those met with in auriferous slates, must have been formed during the most recent geological periods." The above examples are well known and be multiplied, if necessary, but we may confine our enquiries.to places nearer home. At Bendigo occur basaltic dykes which are, in all probability, a consequence of the Tertiary volcanic activity which is such a marked feature of Victorian geology. Cutting across these dykes are auriferous quartz veins, which must necessarily be of still later origin. The occurrence of auriferous pyrites well known. These examples constitute evidence that in Victoria, as well as in other parts of the world, auriferous lode matter was, when conditions were favourable, in process of circulation and deposition well into the Tertiary period. In view of this fact it becomes a question of considerable interest and importance why the whole series of formations 'between the Silurian and Tertiary, occupying large areas and representing immense periods of geological time, should have contributed so little to our gold production. The object of the present paper is to give a brief description of the relations to each other of the Silurian and some of the later formations in the lower portion of the Mitchell River Valley, and to indulge in a little speculation as to the probable.