The student will, however, have some idea of the minuteness of the unit which would then be wanting to complete the square, when he is informed that, if we suppose the whole globe we inhabit to be composed of sand, such that a cubic inch would contain ten millions of grains, a ten-tredecillionth of the globe would be less than the billionth part of one of these extremely minute grains, which part, could the grain be so comminuted, could never be discovered, even by the aid of the most powerful microscope.