Page:Popular Science Monthly Volume 64.djvu/562

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The fan, shown in drawing, is run by steam-engine (not shown) and draws the air upward, from the great chambers of the caverns, through the shaft A. By opening door C, also door R, the air can be forced through corridor M, directly to plenum F, as indicated by arrows marked S2, and distributed through the rooms without passing through condenser. With door C closed the whole volume of air is drawn through condenser B before coming to the fan. Passing through the fan (door in partition at R being closed), the air passes through an auxiliary condenser D to plenum F, whence it is forced by pressure of the fan into all rooms. The air from plenum is forced through a heat chamber, over steam coil, in cold weather, thence through opening into the air supply pipe G and discharged into room H through a register just below ceiling of room. If room becomes too warm, the volume of warm air flowing in pipe G may be reduced or entirely stopped, by pulling cord or chain suspended from the inflow register in room, thus moving valve in pipe G. The movement of this valve permits as much cool air to rise through a lower opening, as warm air is shut off by closing the opening from the coil, or heat chamber. Process last described may be traced by arrows marked S. The outflow of air from rooms may be traced by arrows marked E. Air is forced from room H into vertical duct K, which is continued to top of building permitting air to escape outdoors. The air passes into, through and out of the rooms in volume equal to the filling of each room, in the building every five minutes continuously. In the summer there is, of course, no heat in the steam coils. The air drawn from the caverns being about 54 degrees, when forced into the building, cools the rooms to any degree comfort may demand, however intense the heat prevailing outside.

At my first visit, in the fall of 1901, I saw demonstrated the remarkable volume in which the air enters and leaves each room without creating appreciable draughts, and the fact that the air is practically free from atmospheric dust. Tyndall ('Lectures on Dust and Disease') has shown that if we darken the ordinary room and allow a streak of sunlight to enter, the condition of the atmosphere revealed is such that