The human mind can scarcely comprehend the enormous numbers of these omnipresent atoms without a resort again to the legitimate use of the imagination. A computation of the increase from a parent germ shows as follows: We know that the parent grows until it reaches double its original size, when it constricts itself in the middle like a figure eight and breaks into two individuals. Each of these divides again, and, on account of the rapidity with which this is done, we find them usually in chains or squares. The warmer the air, the faster this proceeds, and at the temperature of the body the entire life history of a germ, from the time of fission of the parent to the time of his own subdivision into two new individuals occupies less than one hour. This gives us a known quantity for our problem. Let us look at the result. From a single germ increasing by the power of two each hour, we have at the end of twenty-four hours 16,777,220; at the end of two days the number has increased to 281 billions, and in three days to the enormous number of 48 trillions, and in one week the number can only be expressed by figures of fifty-places. In order to make this number comprehensible, let us figure the mass and weight of this, the result of a single bacterium. A single Bacterium Termo has an average width of 1/1,000 mm. A cubic mm. would therefore contain six hundred and thirty-three millions, and in one day would be one-fortieth full. At the end of the following day there would be required 444,570 such cubes to contain the product of the parent, or say half a litre. Suppose the seas of the earth cover two-thirds of its surface with a mean depth of one mile, the aqueous product would be 929 million miles. Now, our parent germ and its product would in five days completely fill this space. More wonderful still is a gravimetric estimation. Suppose we call the specific weight of the parent germ the same as water, which cannot be far from right, it would appear that the parent weighs, or his equal bulk of water weighs, 136 millionths of a gramme; in forty-eight hours, 442 grammes; in three days, nearly 7½ million kilograms; and, inside of thirty days, the weight of the earth itself.