Abstract: An evaporative cooler pad consisting of loosely packed, randomly oriented fibers of balsam poplar (Populus tacamahaca) also known as balm of Gilead, which are generally ribbon-shaped and which are coated with a thin layer of Portland cement that is water-absorbent and has a granular surface. Balsam poplar has the unique property of forming a firm, adherent bond to the Portland cement, and the cement-coated ribbons of wood absorb and diffuse moisture over their entire surface in the manner of a blotter, so that they become uniformly damp without being excessively wet. The damp, Portland-cement coated fibers present a large surface area of moisture to the air, thereby facilitating rapid evaporation for good cooling effect, without allowing the air to pick up and carry along any fine droplets of water, which would make it wet. The damp, cement-coated fibers also cool without adding appreciably to the humidity in the air.