of fire is reduced to a minimum, for no part of the pipes can have a higher temperature than 212° F.; and an equable temperature can be readily maintained, as the heat is easily regulated and controlled. The furnaces are economical, as any fuel capable of generating heat sufficient to boil water can be used. In fixing the pipes, a word of caution may be given against laying them in trenches in the floor with surface gratings. Not only is more heating surface necessary, for a great part of the heat is radiated into the brick channels which hold the pipes, but they are most unsanitary. Dirt, dust, and filth fall through the grates and collect around and under the pipes, where it is difficult to be removed, and as soon as the pipes get warm, a constant current of fine dust ascends with the heat and contaminates the air. Hot-water pipes should in all cases be run on brackets around the room, so that the dust can be wiped from them daily with a wet cloth. Radiators, or coils and stacks of pipe, should be fixed near the doors in entrance halls, and adjoining all fresh air inlets, to warm the air entering the building. The boilers and main pipes used to convey the water beneath the floors should be covered with some good non-conductor.
The ventilation of libraries is a difficult problem which does not seem to be yet solved. In this country but few libraries have adopted mechanical methods; nearly all rely upon natural ventilation, and the same inlets are expected to be as satisfactory in July, when the outside air is hotter
