Mohave County miner., 1883-02-11
s&IEE kN KENES.

There are two principles which are
 relied upon to ventilate a mine. That
 of heat expanding the air and the ab hoTence of a vacuum by nature.
 Add to these a system of pumping or
 forcing air into a place, and we have
 the three ideas upon the expansion
 of which into practical methods all
 ventilation of mining properties de- ! pends. There are various causes
 which develop heat in mines. The
 lamps or candles by the light of
 which the miner works, the heat giv-
 en out by tho bo6ies of the men as
 the result of that work, the oxidation
 of sulphur, if any be present in the
 mineral or in the'walls, being among
 them. There may be, too. the heat of thermal springs, or, if che mine be
 deep enough, that which is found in the rock. If we suppose shaft to
 be sunk, say 2,000 ft., and if in the
 centre of that shaft we placed tube,
 or box, or any substance, wood, for
 example, which runs from the sur
 face Of the ground to the bottom of
 the shaft, there would be at once created circulation of air. The air
 around the sides of the shaft being
 heated by the walls would rise, and
 the vacuum so created would draw
 the cold air down through the box.
 But if We kindled fire below the box, the current of air would be down the shaft and up the box.
 The system of ventilating a mine by heat is simply the one which we have imagined expanded to the ex- tent necessary to ventilate the whole m1ne. If we run off from one side from the bottom of our shaft level of 800 ft in length, and carried the box into the face of it, we would have precisely the same thing taking place as before. The air, as heated by the walls, would travel along the level and ascend the shaft. while the cold air would come through the box. If instead of constructing a box We placed a division in the shaft, cut ting it into two equal parts, as we do so often ia this country, the cold air would descend on one side and the warm air would ascend on the other. Suppose, however, that we had two shafts-one at each end of the level; then the air would come down one, traverse the level and go up the other. The dnection in winch It would travel would depend altogeth- CT upon the size of the shafts or tke amount of heat generated. If the shafts were of unequal size the air would come down the smaller and go up the larger. If it is the same the air would move in the direction of that shaft the centre or the equiIi- brium of heat Wds nearest to. If the center or equilibrium of heat was ex actly in the centre of the level, and if the friction on the air was exactly equal ir each shaft, then We couId | cause the air to move whichever way we pleased by building fire at the foot of the shaft we wished it to as ! cend. Keeping that fire burning fer !. a day would be sufficient to cause the ' air to ascend that shalt in prefereGce to the other for all time, because the ! cold air constantly descending through one shaft Would cool that shaft off and so move the point oi of heat nearer to the other.
 The ventilation of a mine where pumping is not necessary Is merely the expansion of the system which has just been outlined. But there are two most important variatlons possible in the application of this system. We may either take the fresh air in through a box to the or we may take the foul air out. Each has its advantages. Tn the first we find the introduction of the fresh ar and the removal of the foul easier than in the second. In the second the foul air and gases generated by blasts are carried off at once and are rot forced to travel ! through the level to the shaft.
 Rod Tsir1fnO TEan0.seAs-pass+