E.—3

106

The following is a rough estimate of the quantity of coal in the field, it being, I believe, rather under than over estimated :— Waimangaroa Basin ... ... ... ... ... 32,000,000 tons. (High levels ... ... ... ... 36,000,000 „ Ngakawau Basin < Mid levels ... ... ... ... 56,000,000 „ (Low levels ... ... ... ... 16,000,000 „ Total ... ... ... ... ... 140,000,000 „ The coal in theAVaimangaroa Basin is of a very good quality, being a hard sound coal, which forms a very light firm coke, and could be worked with the smallest amount of waste possible. It is, however, very badly situated as regards means of transit, and will, I am afraid, be the last part of the field to be worked, notwithstanding the quality of the coal. In the Ngakawau basin the coal on the high levels is of a good sound quality, but more fragile than that in Coalbrookdale, although it certainly comes next in quality to that. This area possesses the greatest advantages of any for the transit of the coal, a good leading spur running, at a distance of about thirty chains from the face of the coal where the main drive would be put in, with ah easy gradient, to the immediate vicinity of the railway. A self-acting tramway, constructed in three stages, would thus conveniently work the whole of this area, containing 36,000,000 tons of coal, a small winding engine only being required to draw the trucks to the top of the tram. In the middle levels, as before mentioned, the upper part of the coal is crushed, but a very modest estimate of the quantity of good coal gives as much as 56,000,000 tons, which renders this at once the most important part of the coal field. It does not present any great difficulties in the mode of transit, although involving a considerable outlay, as a tramway of about two miles in length would have to be constructed from the Ngakawau to the face of the coal; but as a gradient of 1 in 6 could be got for this, along the line which I have shown on the map, it would be self-acting, and the first expense would be the greatest, and the quantity of coal would fully justify the expenditure. In the lower levels the quantity of coal is not yet proved, and it would be advisable, before commencing to work this area, to put down a few bore-holes to prove the amount of coal. If these prove satisfactory, I think the best means of transit would be down Rome's line, from the face of the coal to where Rome's line crosses the line I have pointed out for working the middle levels ; but this is open to further consideration. With regard to timber suitable for mining purposes, the greater part of this field is utterly devoid of any, with the exception of the low levels and a few patches of no great extent scattered over the field, so that timber would have to be brought to the place, and it becomes a matter of importance to use as little and as light timber as can be employed with safety. This brings me to the question of how these thick seams are to be worked to the best advantage, and I cannot do better than cite a few methods which have been employed under similar circumstances. The " Dudley 10-yard coal " has been worked on a system known as " square work," which consists in putting a main drive in through the lower coal, ventilating it by means of a separate air-head. From this the main workings are opened in the form of squares, fifty yards to the side, shut off by a rib of coal seven or eight yards thick, an entrance being effected through a narrow bolt-hole. These squares are worked out in stalls ten yards wide, leaving pillars ten yards square, and the whole seam is thus worked out at one lift. When the roof begins to break, the square is abandoned, and a dam put in the bolt-hole, thus isolating this deserted square from the main workings. Of course ordinary timbering is useless to support so high a roof, and the work is doubtless the most dangerous that can be engaged in, added to which an unnecessary amount of waste takes place from the crushing of the pillars, and the impossibility to work the coal any longer than the roof will stand of itself. This system has of late years been superseded by the method of working the coal in two lifts, on the long-wall system, with a greatly increased yield of coal; but even this system is hardly satisfactory, as the death rate from falls of the roof in this district still continues to be very high. The most successful system yet adopted is that employed in the Department of the Saone et Loire, where, at Montceau, near Blanzy, the seam is no less than 78 feet thick, which would render it the nearest approach which we can find to our own coal fields. It is entitled " working by remblais." This system consists in taking out horizontal slices of coal about seven feet thick, commencing at the bottom of the seam and filling in the space with stone and earth from the surface. A band of coal of the same thickness as that taken out is left above this, and then another slice taken out and filled in, in a similar manner. After a few months this filling is found to solidify sufficiently to form a roof for the working of the intermediate coal which has been left. The plan of working may, of course, be on the " post-and-stall " or "long-wall" systems, as may be most convenient. As the returns to the Government will, of course, depend upon the quantity of coal exploited, I would respectfully suggest that, before granting mining leases to any companies, a stringent set of rules be drawn up, defining within certain limits the system of working to be employed, as by no other means can the maximum yield of coal be relied upon, and a guarantee be obtained that the mines will not be so mismanaged as to waste a large proportion of the coal, or even render it necessary to close the mine long before such a proceeding ought to be required; and, at the same time, if the workings are not carried on in a systematic manner and with every precaution, life would be endangered to an unnecessary extent. To see these rules carried out, if formed, would necessitate the presence of a resident inspector of mines on the West Coast; but when it is considered that, by charging a royalty of 6d. per ton on the coal, a sum of £3,500,000 would accrue to the Government, the expenses thus incurred would I think be justified. With regard to the further prosecution of the survey, Mr. Denniston is at present engaged on the western slopes of the coal field, where there is some quantity of slip coal being worked by Messrs. Roche and Co, the extent of which yet remains to be proved. It is lying at a high angle, and I am inclined to