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VI. VENTILATION AND HYGIENE. With the attainment of considerable depth in metal-mining operations, and consequent increasing underground temperatures, together with the more extensive use of rock-drills and explosives, the necessity for a stricter standard of ventilation than that at present established by statute appears to be necessary, and this view has been taken by the Royal Commission i which presented its report during the early part of the current year. Samples of mine-air taken by officers of the Mines Dβ] bhe mo anl mines throughout the Dominion, and analyzed by the Dominion Analyst. purity of the air, the conditions are generally satisfactory in Nγ ■■ ;ines. It was found that under the most unfavourable mining conditions —namely, when shovelling commenced after blasting— the maximum quantity of carbon-monoxide obtainabi- the Waihi Mines, 00025 per cent., and from the Eeefton Mines, 0-008 per cent; and as Dr. c recognized British authority, has stated that noticeable symptoms of carbon-monoxide poisoning were never produced with less than 0-02 per cent., since absorption ceased when the blood became saturai imj lively slight extent, it may reasonably be concluded that this gas is nol i in our metal-mines, under normal conditions, in hurtful quantities, and is never p; accompanied by carbon-dioxide. The highest percentage of carbon-dioxide—namely, 3-31 per Led at Thames from a sample taken at the 1,000 ft. crosscut, where this gas oc< lies from the rocks in considerable quantity. The maximum percentage of cai here was 0-97 per cent., being less than the standard, T25 per cent., recommended by the British Royal Commission on Mines aa a proportion up to which men may be permitted to work. It will be seen, therefore, that from the point of view of m> s, New Zealand metal-mines generally satisfactory. The question of underground temperatures, however, is, on the Hauraki Goldfield, becoming ol more importance as depth is attained. It has been found that the rock-temperature at Thames and Waihi is high, equal, in fact, "to that of Comstock, United States America, being at the 1,000 ft. level about 83° Fahr., and the increment of temperature about 1° Fahr. for every 33 ft. descended. As regards humidity, official observations taken at the surface over an extended period show the atmosphere at Waihi and Thames to be often highh ;(ions taken underground by officers of the Mines Department show the mi;: o the extent of 90 per cent, or more. On occasions when the air at the surf at, flu' impoesi bility of reducing the humidity in the mine is appan For the purpose of reducing the temperature of rock-surface c of air is necessary bhan is required to produce, from a quality stan<: ilation : but the ex underground temperature maybe reduced ;h, if the upcast shaft is centrally situated with regard to the mil much ma} ied. i he beneficial effect of constant mechanically produced ventilation reduction in th<temperature of the rock-surfaces in the lowest level Waihi, where a Sirocco fan, having a capacity of about 40,000 cubic fee mute, was recently installed to supplement intermittent natural ventilation; similar benefici Iso been obtained a 1 Thames Goldfield deep levels, where there has been installed a . of 12.000 ft. capacity. For the reduction of humidity at the Comstock ; Jon to the introduction of large volumes of fresh air, the underground crosscuts and le c existed were frequently lined with timber, and the drainage-water was conveyed in boxes, which measures were found beneficial. With the attainment of depth it may eventually be found nee; adopt similar methods here. The following proposed standard of ventilation has been recommended by the Royal Commission for metal mines in New Zealand : — " An adequate amount of ventilation shall be con dilute and render harmless noxious gases to such an extent that all shafts, crosscuts, levels, etopes, stables, and all working-places shall be in a fit state for working and pa: " The quantity of air in the main current and in c d at such may be determined by the Inspector, shall at least once in ever)- m<; ] in a book to be kept for the purpose at the mine, and the ordinary number of | i< h split a< one I inie shall also be entered in such book. " For the purposes of this section a place shall not be deer i.-jng or passing therein if the air contains more than 1 per cent, of carbon- than 19 per cent, of oxygen : Provided that the Minister of Mitics may exempt anyeiine or mines from the f< provision on the ground that they are liable to unavoidable vitiation by carbon-dioxide from the rocks during the early s of development. The maximum temperature of the air in any working-place, measured by a wet-bulb thermometer, shall not exceed 80° Fahr., unless firing of explosives has occurred in such place not more than twenty minutes previous to the observation of the thermometer, but the Inspector may, in writing, allow a higher limit of temperature if satisfied that it is impracticable to maintain the temperature below the abovementioned standard, in which case the Inspector shall notify the manager in writing to reduce the temperature of the air below the standard, and if such is not complied with within seven days he shall determine the number of hours, not exceeding six, for whicl son shall be employed in any such working-place within eight consecutive hours, and the number of hours so determined shall not be exceeded for a period of three calendar months whatever the temperature may be during that period. " Regulations under the Mining Act shall provide for the classification of mines according to the amount of noxious gases in the working-places and to the temperature of the surrounding rocks, and the amount of air passing into a mine shall be such amount proportionate to the number of men and animals employed underground in the mine as may be prescribed by the regulations respecting mines of the class to which the mine belongs