From the Cataract of the Macquarie, a flat extends to the marshes in which that river exhausts itself. From the midst of this flat Mount Foster and Mount Harris rise, both of which are porphyritic: but as I have been particular in describing these heights in their proper place, any minute notice of them here may be considered unnecessary. We will rather extend our enquiries to those parts of the colony upon which we shall not be called upon to remark in the succeeding pages. Returning to the coast, we may mark the geological changes in a line to the S.W. of Sydney; and as my object is to extend the information of my readers, I shall notice any particular district on either side of the line I propose to touch upon, which may be worthy of notice. It would appear that the first decided break in the sandstone formation which penetrates into the county of Camden, is at Mittagong Range. It is there traversed by a dike of whinstone, of which that range is wholly composed. The change of soil and of vegetation are equally remarkable at this place; the one being a rich, greasy, chocolate-coloured earth, the other partaking greatly of the intertropical character. In wandering over them, I noticed the wild fig and the cherry-tree, growing to a much larger size than I had seen them in any other part of the colony. Upon their branches, the satin bird, the gangan, and various kinds of pigeons were feeding. Birds unknown to the eastward of the Blue Mountains, were numerous in the valleys; and there was an unusual appearance of freshness and moisture in the vegetation.