13. Relation of Heat to the Forms of Matter.—Some kinds of matter are seen in all the three forms. Whether these shall assume one form or another depends on the amount of heat present. Thus when water is solid, ice, it is because a part of its heat is gone. Apply heat, and it becomes a liquid, water. Increase the heat to the boiling point, and it becomes steam, or an aeriform substance. Alcohol has only two forms—liquid and aeriform. It has never been known to be frozen. Iron is usually solid; but in the foundry, by the application of great heat, it is made liquid. Mercury is liquid in all ordinary temperatures; but it often becomes solid in the extreme cold of arctic winters. A mercurial thermometer is of course useless under such circumstances, and the alcoholic thermometer is relied upon to denote the degree of cold. The difference between mercury, water, and iron in regard to the liquid state is this: It takes but little heat, comparatively, to make mercury liquid, while more is required for this condition in water, and much more for it in the case of iron.
14. The Nature of Matter Unknown.—What now, let us inquire, do we know of the nature of matter? Can we say that we know any thing of it? We may observe its phenomena, and learn its properties; but with our most searching analyses of it we can no more determine what matter is than we can what spirit is. Newton supposed "that God in the beginning formed matter in solid, massy, hard, impenetrable particles." This he believed to be true of liquids, and even of gases, as well as solids. In the gas these hard particles are much farther apart than in the solid. The supposition is a very probable one; but if it be true it does not let us know what matter is, for it leaves us in the dark as to the nature of the particles. Newton farther supposed that these particles have always remained unaltered amidst all the changes that are taking place; these changes being occasioned by "the various separations and new associations and motions of these permanent particles." When, for example, any thing is burned up, as it is expressed, not one of these particles is either destroyed or altered, but they merely take on new arrangements. Though most of the substance has flown off in the form of gas, the ultimate particles composing the gas are the same now that they were when making a part of the solid substance; and they may soon again become a part of some new solids. Such changes in the forms of matter are every where going on; and when you become acquainted with Chemistry, in the Second Part, you will be familiar with them.
15. Atomic Theory.—These ultimate particles of matter are so minute that they have never been seen by man. The smallest particle that can be seen with the most powerful microscope is probably made up of very many of them united together. These ultimate particles we term atoms; and the theory in regard to the composition by them of different substances is called the atomic theory. The atoms of different substances are not supposed to be alike, but to differ in both size and weight. This theory will be more particularly noticed in the Second Part.
16. Imponderable Agents.—There are certain agents—light, heat, electricity, etc.—which are supposed by some to be forms of matter. If they are, they are exceedingly attenuated; for their presence, as has been proved by many experiments, never adds in the least to the weight of any substance. They have therefore been styled imponderable agents. Their agency is of great importance and very active, producing every where constant changes. Two of them—heat and light—are obviously and immediately essential to life. What their real nature is remains as yet an entire mystery.
[CHAPTER II.]
PROPERTIES OF MATTER.
17. Variety in the Properties of Matter.—All matter has properties or qualities. Some of these are different in the different kinds of matter. Thus its three forms have different properties, as you saw in Chapter I. There is variety also in the properties of substances of the same class. Thus liquids are unlike each other in some respects. Some, for example, are lighter than others. Oil is lighter than water. Gaseous substances also differ in this and in other respects. But the variety in the properties of solids is greater than in those of gases or liquids. This will appear as I proceed.
18. Divisibility of Matter.—Any visible portion of matter can be divided into parts. Even if it be so small that you can see it only with a powerful microscope, it could still be divided if you could have an instrument sufficiently fine for the purpose. Divisibility, then, is said to be a general property of matter; that is, a property belonging to all kinds of matter.
19. Examples of Minute Division of Matter.—There are numerous examples in which the division of matter is carried far beyond that which can be effected by any cutting instrument. Some of these I will notice:
A gold-beater can hammer a grain of gold into a leaf covering a space of fifty square inches. So thin is it that it would take 282,000 of such leaves, laid upon each other, to make the thickness of an inch. And yet so even and perfect is this thin layer of gold, that when it is laid upon any surface in gilding it has the appearance of solid gold. A fifty millionth part of this grain of gold thus hammered out can be seen by the aid of a microscope which magnifies the diameter of an object ten times. But the division of gold is made even more minute than this in the manufacture of the wire of gold-lace. It is done in this way: A bar of silver weighing 180 ounces is covered with a layer of gold weighing an ounce. It is then drawn through a series of holes in a steel plate, diminishing in diameter, till it at length comes out a very fine wire 4000 feet long. Each foot of it then has only the one 4000th part of the ounce of gold, and yet the silver is well covered.