The arrangement of facts discovered by actual experiment and called " science" is conveniently divided into Physics and Chemistry. Physics treat of the changes of matter, without any regard to it internal construction. Thus the laws of gravitation and cohesion belong exclusively to physical science, because they act with total disregard to the composition of a substance. Chemistry, on the other hand, teaches us the composition of the various forms of matter, and the changes they can undergo one with another. Water, speaking with regard to its physical or natural characteristics, is a colorless, mobile liquid, boiling at 212, and freezing at 32, not capable of compression, and many more similar peculiarities. But chemically speaking, water is a compound of so much hydrogen and oxygen, capable of entering into many combinations, and of causing changes in other forms of matter. The science of chemistry has undergone a technical division into organic and inorganic, but in nature there is really no such division —it has only been adopted for convenience of study and expressioa ; for the two classes of substances (organic and inorganic) BO lap into each other, that the boundary line is daily becoming more faint, and will in time, por-haps, vanish altogether. Probably the most safe definition of organic! chemistry that can be given in contradistinction to inorganic, is contained in the assertion that the former branch of the science treats of those bodies which are, directly or indirectly, the products of the vital process in animals or vegetables; and this definition is now tacitly admitted by all chemists, although some substances have been produced in the laboratory which are especially peculiar to the process of animal secretion, as for example, urie acid.