The microscope has shown that a drop of water though it may appear to the naked eye to be perfectly clear, is swarming with living beings. According to Ehrenberg, a cubic inch of water may contain more than 800,000 millions of these beings, estimating them only to occupy one fourth of its space; and a single drop, placed under the microscope, will be seen to hold 500 millions; an amount, perhaps, not so very far from equal to the whole number of human beings on the surface of our globe!