"We know that we have earth, air, water, and we have seen in Chapter II that the earth's crust is made up of many substances, rocks, coral reefs, clay, marl, feldspar, quartz, limestone, granite, etc., etc. These substances are composed of small particles, or elements, and are called minerals or inorganic substances. There is another class of substances, called organic, that are derived from living things or beings. These are also taken apart or separated into their elementary substances. As plants or animals, all such elementary substances have received the name organic substances because plants and animals have organs of reproduction, hence the name. The taking apart of any substance into its constituent elements is called analysis by chemists. The same elements can also be put together to produce various substances; that is termed synthesis. Chemists have adopted a name for each of the elements, and these names are represented by symbols, or letters. Compound substances may contain two or more elements. When the composition of a substance is determined by splitting the compound into its elementary constituents a chemical analysis of that substance is said to have been made; and if the proportions by weight in which each of the constituents is present be determined, a quantitative analysis of the substance has been made, etc. By chemical action, we signify that which occurs when two or more substances so act upon one another as to produce a third substance differing altogether from the original ones in properties; or when a substance is brought under such conditions that it forms two or more bodies differing from the original one in properties. Chemistry is called an experimental science. In investigating all the materials within his reach, whether solid, liquid, or gaseous, whether contained in the earth, sea, or air; whether belonging to the mineral, animal, or vegetable creation, the chemist finds himself obliged to divide substances into two classes: (1) compound substances--those which he is able to split up into two or more essentially different materials; (2) elements or simple substances--those which he is unable thus to split up, and out of which nothing essentially different from the original substances has been obtained.