Mr. Beadle has recently patented his improved fan and system of ventilation ; and, from a personal investigation of the plans and their effective operation, we have no hesitation in stating that his system is the most perfect, effective, safe, and economical, —in a word, more available than any other mode of ventilation, and far superior in every respect to the furnace method.
The facts we arrive at, after a full consideration of mine-ventilation in all its bearings, which, however, we have but briefly noticed in the foregoing pages, may be summed up in a few words: 1. The areas of the air-ways should be proportionate in size or diameter to the quan tity of air required, since the increase of air in a given area is only accomplished by an eightfold increase of power.
2. The air-ways should not be contracted at any point to a less general diameter than the column requires, moving at a uniform speed, or than the area of the downcast shaft and main inlet avenue ; because the increase of density and friction, and, consequently, the power required to propel the column, are in proportion to the contraction of the area.
3. The air-ways are most effective when they are uniform and free from projecting and obtuse angles; because air, which moves in a solid body, impinges or drags on all rough surfaces, and, consequently, the more smooth the surface of the passages the more freely will the currents of air pass through the mine.
4. The longer the column of air, the greater will be the force necessary to move a given column; and the smaller the areas of the passages, the greater the friction and velocity of the air. But the more the air is divided and the greater the areas of the
auxiliary passages, the less will be the friction and power required to move a given column, unless increased beyond the area necessary for the full atmospheric expansion: consequently, the shorter the currents, the larger the ways, and the more direct the courses, the more effective will be the ventilation.
5. In order to convey pure air to each breast and to supply each miner with a healthy atmosphere, as well as to shorten the current, decrease the drag of the column, and prevent danger, it is essential that the air be "split" and conveyed by special currents into the respective workings of the mine, and that the returning impurities should pass into the return air-ways without coursing through other workings. To do this effect ually, it is necessary that the mine should be laid out in districts or "boundaries," as described in a former chapter.
6. The permanent air-courses should always be parallel with the permanent avenues of the mine, and should never run through the excavated and abandoned parts, except for temporary purposes. "Gas drifts," however, should always be kept open, for the escape into the return air-courses of any gas which might accumulate in the "goaves," as shown by the arrows in several of the illustrations given.
7. Mechanical ventilation, as illustrated by the exhausting-fan, is the most available mode known, and, for present purposes, the most perfect and economical that can be devised.