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this must be done with caution —to neighbouring areas, particularly to the Rosemont and Silverton hills, in the eastern part of the Waihi Borough. The Owharoa, Waitekauri, and possibly the Waihi Beach lodes may also be richer in depth than in the bottom levels of the mines that have been worked in those districts. The lodes of the Waihi district have been found to occupy fault planes or zones, and the knowledge of their structural relations thus obtained helps to support the belief that a study of the widespread faulting in the Hauraki Peninsula will aid in the location of valuable mineral lodes. The hypothesis that the platy or lamellar quartz of the Ohinemuri mines is pseudomorphous after calcite has been demonstrated to be erroneous, and consequently the deductions made from it have no validity. Since similar quartz occurs in many " Tertiary " goldfields, and in almost all cases has been supposed to be " pseudomorphous," the evidence brought forward at Waihi will be of value elsewhere. The period of mineralization or lode-formation has been approximately ascertained, and the assumption often made that the Hauraki and similar lodes are the result of more than one period of mineralization has been shown to be unnecessary, and probably in great measure erroneous. Similarly, the assumption that a " critical level " of ore-deposition, determined by conditions of temperature and pressure, exists at a moderate depth is totally unproved, and probably incorrect so far as minable depths are concerned. Several other time-honoured hypotheses are endangered if the conclusions reached are approximately correct. The investigations made at Waihi therefore tend to show, in opposition to many authorities, that the future of " Tertiary " goldfields in depth is not necessarily oblivion. On the other hand, both at Waihi and elsewhere, serious difficulties are caused by the great expense of working deep mines in volcanic rocks, intensified by the rapid increase of temperature with depth. 10. Maratoto District. (Summary of Reports by P. G. Morgan). During the past three years the writer has made several visits to the Maratoto district, which lies in the upper part of the Hikutaia Valley, and can be reached by road from Hikutaia Railwaystation, or by tracks from Waitekauri and Golden Cross. Reports have been furnished on the claims formerly known as the Silverstream, Tellurides Proprietary, &c, being prospected by Ohinemuri Gold and Silver Mines (Limited), and on the Majestic Claim, which includes areas formerly known as the United or Maratoto Consolidated Claim (Peel Creek), Walker's Maratoto, &c. These various claims are fully described in Bulletin No. 15, pages 100-104, and not a great deal can be added to the statements there made. Faulting is prevalent in the Maratoto district, and no doubt the main lodes occupy fault planes and zones, as in the Waihi district, but not enough field-work has been done to enable the faults to be mapped. Several of the Maratoto lodes are large and persistent bodies of veinstone, which near the surface have yielded a few thousand tons of ore, some of which was very rich in silver, but none was rich in gold. The ratio of silver to gold commonly exceeds 100 to 1, and in the richest ore may exceed 1,000 to 1. The veinstone of the United Mine contained more gold than most Maratoto stone, but was low in silver, and on the whole was not payable under the conditions of former days. The silver was mainly in the form of sulphide, and there was also some telluride. Visible gold, so far as the writer knows, has not been reported, but the " oxidized " veinstone commonly gives a tail of gold in the dish. The metallic sulphides present are mainly pyrite, with a little ohalcopyrite, and possibly some zinc-blende and galena. In the upper levels, apart from the rich silver-ore, the veinstone is chiefly low-grade " oxidized " quartz, much of which is platy or lamellar, and well stained by oxides of manganese and iron. Some of the oxidized quartz, however, may assay half an ounce of gold to the ton, and even more. That large amounts of calcite were formerly present is obvious, and in the lowest levels on the Camoola lode and the United lode (Mcßrinn's Creek workings) the veinstone is mainly a massive intergrowth of the two minerals, quite clearly contemporaneous, as at Waihi. This material in places is traversed by bluish veinlets containing silver sulphide and speckled by ohalcopyrite. Where this is so, it contains from a few ounces upward per ton in silver, and also a little gold. Mining in the Maratoto area has been unsuccessful, and Bell and Eraser are clearly adverse to its future prospects. One of their lines of evidence, that founded on the presence of abundant calcite in the primary veinstone, is open to challenge, but on the whole the burden of disproof is on their opponents. It is clear that the upper levels of the Maratoto and other lodes have been leached by descending solutions, and this has led some persons of sanguine temperament to believe that rich secondary ores will be found in depth. Such ore, however, will not occur in quantity sufficient to reward the miner if the lodes originally were very low-grade. The available evidence points in this direction, but it is not conclusive. Hence, in order to determine the probability or otherwise of ore in depth, a detailed re-examination of the Maratoto district by an experienced mining geologist is needed. To determine the probability of ore in the Maratoto district by analogy with Waihi would be dangerous and useless. The writer has to point out that, while the genesis of the mineral lodes in the two districts is similar, there are important differences in several respects quite sufficient to invalidate the analogy that is sought to be drawn. One must not assume that all or even a majority of the Hauraki lodes were payable or nearly payable when first formed, as may have been the case at Waihi. Maratoto and other mining districts must stand or fall on their own merits. It is important to decide whether the small but rich patches of silver-ore that have been worked at Maratoto are primary or secondary. If they are in the main primary, hope of rich ore in quantity at greater depth would be justifiable ; if they are secondary, as appears to be the case, only similar small shoots are likely to be found by further exploration, either laterally or in depth.

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