�� ��Imagine fourteen Woolworth buildings, each of them 792 feet in height, piled one on top of the other. What a column! And yet that would be the height of the stack made by piling the 275,000 copies con- stituting this December issue of the Popular Science Monthly one upon another. The topmost number would be lost in a cloud at a height of 11,000 feet. Airplanes do not reconnoiter at heights much greater.