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Glen Afton Colliery.—The development of this mine was commenced eight years ago, and during the past year the company despatched 167,632 tons of coal, principally to the dairy factories and shareholders of the New Zealand Co-operative Dairy Co., Ltd., the owners of this colliery. The mine equipment has been increased correspondingly with the advance of the mine-workings. The main headings have reached a distance of one mile and a quarter from the entrance of the mine. The pillars are being removed from A section, one of the first sections to be turned off the main haulage-road. The crushing movement which rode over the pillars of D and G sections during the year 1926 appears to be settled. Several of the affected pillars on the airway side have been strengthened with facings of brick walls erected from roof to floor along the pillars between the stoppings. Pillars of 1 chain square and barriers from 1 chain to 2 chains of solid coal have been formed and provided for the support of the increasing roof-cover in all the recently developed districts. The headings in K and J sections, through the upthrow fault, have been rapidly advanced to open out a widely spread area for working-sections. The faces in these districts have been advanced to the extent that there is now a difficulty in maintaining an adequate standard of ventilation. The position has been temporarily improved by the introduction of two auxiliary fans for use in boosting the ventilation. Two downthrow faults, of 20 ft. and 30 ft. displacement, have been encountered in the main heading. The corners of the pillars in the majority of the places are being supported by timber props and laths, thus affording protection from falls from pillar-sides. The coal-seam generally is liable to spontaneous combustion, but with the adopted panel system of barriers, large pillars, and few openings in each district I would expect a high percentage of coal from the extraction of the pillars under a roofcover of 400 to 500 ft., as proved to exist over the area. The surface plant has been increased b}' the installation of a new steam boiler and another generator for the production of electric current to operate the subsidiary haulage machinery in the mine. Graham's Colliery (Co-operative Party).—Twenty men are employed in and about the colliery for an output of 50 tons per day. A drive to the surface on the rising outcrop has considerably improved the ventilation of the pillar workings. At the same point a water-free drive has been driven under the seam to facilitate the drainage of the main dip. The pillars have been successfully extracted under ideal pillaring conditions, consequent to the driving of narrow places, 6 ft. wide, in the first workings. Pukemiro Junction Colliery (Croivn Lease: Co-operative).—Headings of small dimensions and large pillars were adopted in the system pursued in opening out the mine. When coming back with the pillars the roof-weight has no effect on the workings, and a high percentage of coal is won from the pillars. The output of 40 tons per day is jigged down to the rail way-wagons at Pukemiro Railway-siding. Waipa Colliery.-—No. 1 and No. 2 sections have been extended from the main dip in a solid area of coal. The timbering of the roofs consist of bars set systematically, and with occasional props set along the brattice side of the places. The pillars are being extracted in No. 3 section under a progressive roof-pressure exerted by a roof-cover of 300 ft. of claystone. The pressure at some points has carried weight over the coal pillars and caused the roof to fall in the roadways to the extent that many fresh roadways have to be made through the falls in order to recover the pillars. A solid barrier has not been provided along the main haulage-road, and a large number of openings will require to be sealed off to prevent heating in the goaf. The humidity of the mine atmosphere was tested by the following hygrometric observations : No. 1 section —65° wet, 66° dry ; combined intakes —66° wet, 67° dry ; No. 3 pillar section — 73° wet, 75° dry : indicating an appreciable increase of temperature as the result of pillaring operations. The ventilation system was improved by providing three separate ventilating districts in the mine. The dust on the roadways was sampled and analysed on several occasions in order to ascertain the conditions of the mine in respect to the inflammability and ignitibility of the coal-dust on the roadways. Waikato Extended Colliery.—Early in the year the company operating this colliery secured a lease of a portion of the old Waikato Mine workings. When preparations were being made to extract the barrier coal lying between the properties a fire broke out in the old workings of the Extended Colliery, and the mine was subsequently sealed up for a period of three months. Several places were opened out in the southern area of the Waikato property. The seam contains numerous clay backs, and is inferior in quality to that mined in the Extended area. Towards the end of the year the fire area was recovered, and several pillars were extracted against the goaf to allow the roof to fall and so cover the goaf ends with fresh falls of roof stone. Bords and headings of the solid workings were 14 ft. high by 14 ft. in width, consequently no suitable positions for stoppings can be obtained against the waste, and the cost of each stopping is very high. The output is distributed along the Waikato River depots by river-steamers owned by the owners of the colliery (Roose Shipping Co., Ltd.). Huntly Brickworks.—This fireclay openface, developed to supply the Huntly brickworks with suitable clay for making building brick, firebricks, tiles, &c., has been safely worked during the year. Taupiri East Colliery (Auckland University Council Endowment Lease). —Prospecting to the rise of the seam revealed an area, of coal destroyed by prehistoric fire. The seam is 18 ft. in thickness at the crown of the terrace, and is reduced to burnt ash where it is exposed in the gullies. Operations are confined to the driving of headings in thick coal. A pump operated by electric motor, has been installed in the mine. The output is conveyed by motor-lorry to Huntly Station, a distance of four miles. Campbell Colliery, Whatawhata (Crown Lease). — During the past three years the mine has been operated by a small party holding a sublease from the company to work the mine on a royalty basis. The agreement to work the mine proved to be unsatisfactory. The roof-supporting pillars were left small and badly shaped, and generally the system of mining pursued by the party was not conducive to the interest of the owners, nor to the development of the mine in regard to provisions which would enable the company to remove the pillars without risk of crushing and fires. The agreement was terminated at the end of the year, and the company has since made arrangements to take over the control and management of the mine. The output is carted by road to Hamilton, a distance of eleven miles. Renown Colliery, Waikokowai. —The colliery is situated about three miles west of Rotowaro Railway-station. The output stage was reached in the month of June, and since that date 26,555 tons of coal have been obtained from the top seam, which was first exploited, as it was conveniently situated to the entrance of the mine. The main dip heading was extended 8 chains on a gradient of 1 in 6 through stone to reach the bottom seam, proved by boring to exist ahead over a large area. The bottom seam is a hard compact coal of clean appearance similar in quality to the coal mined in other Waikato mines. Having regard to the susceptibility of the seams to spontaneous combustion, it is intended to develop the mine on the approved panel system. The seams are lying practically level, and it is proposed to open out 5-acre districts with 1J chain barriers round three sides of the panel. Pillars are to be not less than 1 chain square, bords and headings are to be 12 ft. wide by 8 ft. high, and airways and roadways are to be amply dimensioned to provide roomy passages for ventilation and haulage. The output during the year was obtained from the top seam from places almost entirely mined by the operations of an Arc Wall coal-cutting machine. It is capable of cutting twelve places in an eight-hour shift, and the daily average output per miner filling from the machines is 12'2 tons, compared with 6 tons per miner in places where the cutting is done by hand. No difficulties have been encountered in operating the two and a half miles of endless-rope tramway constructed over undulating country to connect the mine with the Government railway at Rotowaro. Electric power for the colliery is obtained from the Central Power Board, and the following description of the installation may be of some interest : The power supplied is alternating current at 400 volts, 50 cycles. There are two substations, one at Rotowaro and another at the mine. Rotowaro station consists of an incoming feeder panel of 300 amp. capacity ; a panel for screening plant. 100 amp. capacity ; and a panel for surface haulage plant of 250 amp. capacity. The capacity of the haulage plant is 100 tons per hour at a speed of two and a half miles per hour, and the plant is operated by a 150 b.h.p. slip-ring induction motor. The screening plant is driven by a4O b.h.p. slip-ring motor for main gear, together with a 6 b.h.p. motor for raising jibs. The capacity of the screens is 800 tons per day. At the mine substation there are four panels incoming, 700 amp. ; mine circuit, 250 amp. ; surface plant, 150 amp.; fan circuit, 80 amp. Power is conveyed into the mine by bitumen-insulated sheathed steel-armoured cables to supply