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the surface of the supposed source of the petroleum increases in that direction. Also, the possibility of the discovery of petroleum is perhaps more hopeful (than elsewhere in the interior) around Mahoenui, in the neighbourhood of the Awakino and Mangaorongo rivers, where the lower measures of the Tertianes are brought, by down-folding, nearer the earth's heated interior. From the above notes it will be seen that it would be, in the writer's opinion, distinctly unwise to commence boring for oil in the Mokau country, or, in fact, anywhere northward of Tongaporutu unless more hopeful indications of petroleum than those already observed are discovered. THE RETARUKE COALFIELD. 1. Introduction. During the winter of 1909 information reached the Head Office of the Mines Department that coal had been found in the country adjoining the Main Trunk line to the westward of Waimarino and Erua stations. Soon afterwards instructions were given the writer to visit the locality, with a view to ascertaining whether or not the reported coal actually existed. Accordingly, early in December a brief visit of inspection was made; but on this occasion, as the guide, a settler living near Erua, was unable to point out any coal occurring in situ, and as the flooded state of the creeks prevented any detailed personal prospecting, it was impossible to ascertain more than the fact that coal-bearing measures were widely distributed in the neighbourhood, and that float coal occurred in numerous tributaries of the Retaruke, as well as in the main stream itself. During February and the first three weeks of March, following the receipt of further instructions from the Under-Secretary of Mines, the area was somewhat carefully examined by the writer, assisted by Mr. H. S. Whitehorn, chainman of the staff of the Geological Survey. To Mr. Whitehorn was left all the topographical work, the prospecting for coal, and much of the detailed geological examination. However, the writer, under whose control the work was conducted, visited most of the principal coaloutcrops, of which some sixteen were located during the progress of the survey. The locality had been recently surveyed for land-settlement purposes by the Lands and Survey Department; but, as these surveys did not include a traverse of the numerous streams, where alone the coal usually appears, it was necessary for Mr. Whitehorn to survey the creeks in order to accurately place the various coal-seams which were discovered. This proved by no means an easy task, owing to the extremely gorgy nature of the main Retaruke, and to the many steep waterfalls on its tributaries. The tracing kindly given by the Lands and Survey Department proved of great service, and to the fixed pegs placed thereon were tied the stream traverses. On the map accompanying this report it will be observed that the streams were surveyed only as far up their valleys as the coal-outcrops, whilst, above, their courses were merely sketched in. In sampling the various coal-exposures some difficulty was experienced in getting a clean face, the coal naturally being much weathered and decomposed on the surface. In no case could a really fresh surface be obtained, and to fully prove the quality of the coal at the various outcrops a drive would have to be put in for a chain or more in each case. It will be readily understood that the quantity of ash in the coal must be higher at the surface than farther in, since much fine silt carried by the water ever percolating downward at the surface is deposited there in fine layers between the laminse of coal. The amount of water in the decomposed coal is naturally, too, greater at the surface than away from it. Samples were analysed from most of the coal-outcrops examined. These were taken from cuts made from roof to floor of the seams, and consequently included much of the impurity in the stony and shaly bands, which are present in greater or less degree in all exposures seen. Where the size and general quality of the coal-outcrops seemed to warrant it, samples were also taken for analysis, picked free from " stone." In these cases it is thought that the impurities can perhaps be readily separated from the good coal in actual mining, as has, unfortunately, to be done in so many mines. In general terms the Retaruke coalfield may be said to extend westward from a meridional line lying about a mile westward from Erua Station, and possibly rather more from Waimarino Station. Its westward, northern, and southern confines are as yet not known, but it is thought that when geological investigations have been prosecuted further in these directions, extensive coal-beds will be found. The examinations so far conducted extended down the Retaruke from its headwaters as far as Mr. A. B. Tylee's whare, situated about ten miles west of Waimarino. It must be evident that in an area so densely forested and in many parts so highly inaccessible as the Retaruke coalfield, by no means all the outcrops of coal were discovered in the brief period covered by the Survey's investigations. However, it is thought that sufficient exposures have been located to indicate the presence of a coalfield of some promise. 2. Character of the Topography. Physiographic-ally considered, the Retaruke coalfield forms part of the Wanganui coastal plain. The plain is here elevated to a general height of over 2,000 ft., and, though almost flat-topped, it has a very gentle inclination towards the west. The densely forested nature of the surface of the plain, and of the numerous valleys incised therein, stands in marked contrast to the tussock-clad Waimarino Plains, which border the coastal feature to the east, and, surrounding the volcanoes of Ruapehu and Ngauruhoe, extend eastwards to the Kaimanawa Ranges. In the area now being described, the Retaruke and its tributaries have deeply dissected the coastal plain. The narrow and \J -shaped valleys are everywhere bordered by steep slopes descending from the level of the plain. Alluvial flats along the course of the Retaruke and its tributaries practically do not exist in the area under revision, though furtheT down the Retaruke. towards the Wanganui, they are fairly extensive.

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