This is a property possessed by all bodies, and means their capability to be separated into parts. It was formerly a question among philosophers whether matter was capable of being divided ad infinitmn, or whether there was a limit beyond which matter could not be divided. The question is incapable of direct solution, and fortunately science does not require that it should be known; but the extent to which subdivision has been carried in the arts is prodigious. In the gilding of buttons, five grains of gold, which is applied as an amalgam with mercury, is allowed to a gross ; so that the coating left must not be more than the 110,000th part of an inch in thickness. If a piece of ivory or white satin be immersed in a solution of nitro-muriate of gold, and exposed to a current of hydrogen gas, it will be covered with a surface of gold not exceeding the ten-millionth of an inch in thickness. A single grain of blue vitriol will give an azure tint to five gallons of water. In this case the copper must be attenuated ten million times, and yet there is sufficient in each drop of water to give it color. Odors are capable of still further diffusion : a single grain of musk has been known to scent a room for twenty years. Animal matter likewise exhibits many instances of wonderful subdivision. The milt of a codfish, when it begins to putrify, has been estimated to contain a billion of perfect insects, so that thousands of these little lives could be lifted on the point of a needle. One of the infusorial animalcules found in duckweed is ten million times smaller than a hemp seed ; and another, discovered in ditch water, appears in the field of a microscope a mere atom endowed with sentient life, and millions of them play, like sunbeams, in a single drop of liquid.