DR. COMSTOCK, I have examined your Treatise on Natural Philosophy with considerable attention, having used it as a Text Book in the Grammar School, immediately on its publication. With this knowledge of its contents, I have no hesitation in pronouncing it the best work on this subject, for the use of Schools and Academies, with which I am acquainted, and therefore hope to see it extensively introduced. Hartford, June 26, 1830. DR. COMSTOCK, E. P. BARROWS, Principal Hartford Grammar School Dear Sir,-I have carefully examined your System of Natural Philosophy, and am of opinion that it is far superior to any work of the kind now in use. As particular excellencies of this System, I would mention its happy illustrations-the perspicuity, variety, arrangement, and originality of its diagrams, and the addition of much new, interesting, and useful matter. It appears, indeed, to have been a principal object with you, to give the Student correct and definite ideas, and in this attempt I think you have been peculiarly successful. I have been highly pleased with the work my self, and can heartily recommend it to the attention and patronage of the public. OLIVER HOPSON, Principal of the Select School. Hartford, June 1, 1830. From the Teacher of Mathematics and Natural Philosophy in the High School, at Ellington, Conn. Dear Sir, I have examined your "System of Natural Philosophy," and used it as a text-book for one class. I consider it better adapted to the purposes of elementary instruction than any work of a similar kind with which I am at present acquainted. ZEBULON CROCKER. Ellington School, Aug. 10, 1830. GENTLEMEN, I have examined "Comstock's Natural Philosophy," and think it is a book excel lently adapted to communicate a competent knowledge of the various subjects on which it treats. It does not enter into that depth of Scientifical and Mathematical illustration, of which the subjects are susceptible; but it illustrates, in a familiar way, most of the principles of Natural Philosophy, and is enriched with a statement of practical details in that science. It is a book well calculated to be highly useful in our Schools and Academies. GENTLEMEN, Most respectfully Yours, &c. ROBERT BRUCE, President of Western University, Penn. I have examined many of those Treatises of Natural Philosophy that have been pre. pared for the younger classes of Students-Dr. Comstock approaches more nearly to the idea I have formed of what such a work should be, than any I have met with. It is rich in Philosophical facts, its explanations are popular, its illustrations practical, and its language perspicuous. It is perfectly adapted to those students at school that do not take an extensive course of Mathematics, and to those that do, it will serve the important purpose of an Introduction. Yours, respectfully, J. H. FIELDING, President of Madison College. NATURAL PHILOSOPHY. THE PROPERTIES OF BODIES. A BODY is any substance of which we can gain a knowledge by our senses. Hence air, water, and earth, in all their modifications, are called bodies. There are certain properties which are common to all bodies. These are called the essential properties of bodies. They are Impenetrability, Extension, Figure, Divisibility, Inertia, and Attraction. Impenetrability.-By impenetrability, it is meant that two bodies cannot occupy the same space at the same time, or, that the ultimate particles of matter cannot be penetrated. Thus, if a vessel be exactly filled with water, and a stone, or any other substance heavier than water, be dropped into it, a quantity of water will overflow, just equal to the size of the heavy body. This shows that the stone only separates or displaces the particles of water, and therefore that the two substances cannot exist in the same place at the same time. If a glass tube open at the bottom, and closed with the thumb at the top, be pressed down into a vessel of water, the liquid will not rise up and fill the tube, because the air already in the tube resists it; but if the thumb be removed, so that the air can pass out, the water will instantly rise as high on the inside of the tube as it is on the outside. This shows that the air is impenetrable to the water. What is a body? Mention several bodies. What are the essential properties of bodies? What is meant by impenetrability? How is it proved hat air and water are impenetrable? If a nail be driven into a board, in common language, it is said to penetrate the wood, but in the language of philosophy, it only separates, or displaces the particles of the wood. The same is the case, if the nail be driven into a piece of lead; the particles of the lead are separated from each other, and crowded together, to make room for the harder body, but the particles themselves are by no means penetrated by the nail. When a piece of gold is dissolved in an acid, the particles of the metal are divided, or separated from each other, and diffused in the fluid, but the particles of gold are supposed still to be entire, for if the acid be removed, we obtain the gold again in its solid form, just as though its particles had never been separated. Extension.-Every body, however small, must have length, breadth, and thickness, since no substance can exist without them. By extension, therefore, is only meant these qualities. Extension has no respect to the size, or shape of a body. The size and shape of a block of wood a foot square is quite different from that of a walking stick. But they both equally possess length, breadth, and thickness, since the stick might be cut into little blocks, exactly resembling in shape the large one. And these little cubes might again be divided until they were only the hundredth part of an inch in diameter, and still it is obvious, that they would possess length, breadth, and thickness, for they could yet be seen, felt, and measured. But suppose each of these little blocks to be again divided a thousand times, it is true we could not measure them, but still they would possess the quality of extension, as really as they did before division, the only difference being in respect to dimensions. Figure, or form, is the result of extension, for we canno conceive that a body has length and breadth, without its also having some kind of figure, however irregular. Some solid bodies have certain or determinate forms, which are produced by nature, and are always the same, wherever they are found. Thus a crystal of quartz has six sides, while a garnet has twelve sides, these numbers being When a nail is driven into a board or piece of lead, are the particles o. these bodies penetrated or separated? Are the particles of gold dissolved, or only separated by the acid? What is meant by extension? In how many directions do bodies possess extension? Of what is figure, or form, the result? Do all bodies possess figure? What solids are regular in their forms? |