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happens, where we cannot discover the spring, we learn enough, during our research, to raise in our minds a deep and lasting feeling of admiration at the consummate skill displayed in the mechanism itself. The main object of Physical Science is the discovery of the prime mover, or prime movers; the springs, in fact, employed by nature in producing those effects which are daily presented to our view.

My time being limited, I cannot, I think, employ it more usefully, in showing the objects and advantages of the study of Natural Philosophy, than by making some remarks upon the various subjects that are included under this general denomination. My observations shall be comprehended under two heads ;-the Practical and the Theoretical uses of the various branches.

I. I place at the head of Natural Philosophy, as that subject which ought first to be studied, Mechanics. It is that branch which teaches the laws of motion, and explains the action of forces on matter.

With regard to the importance of this study, practically, there can be no dispute. How could our steam engines, our lathes, our cotton mills, our ships, our houses, our infinite variety of machines employed in the arts and manufactures, be constructed, how contrived, by a person ignorant of mechanical science? If constructed, how, without this knowledge, could their effects be calculated; how their various parts proportioned to the work to be done? How much valuable time, how much useless thought, how many vain attempts would have been spared; how much expence avoided, in a multitude of instances of daily occurrence, had the individuals possessed even an elementary acquaintance with mechanics! How many chimerical schemes for perpetual motion would, with even such an acquaintance, be abandoned! For it is notorious that this visionary project is universally attempted by persons, almost, if not entirely ignorant of mechanical principles. To the practical man; to the man who is to devote his future life

to the invention and construction of useful machines, this branch of science must prove invaluable. It will be the mine from whence he must draw his future treasures. This important branch of Natural Philosophy it will be my aim to render as intelligible as possible. Convinced by the experience of some years, devoted to tuition, that mere diagrams and mathematical demonstrations will never make a sound impression on the mind, or carry perfect conviction to the understanding, I shall at starting, that is, during the first year's course, give a series of lectures on the Elements of Mechanics, and the Laws of Motion. These lectures I shall illustrate by such an extensive and complete set of apparatus, as will enable the lowest capacity to master this valuable and important subject; this stepping-stone to all our acquaintance with the operations of Nature. In my succeeding lectures on Mechanics, I shall make our mathematics available in arriving at certain conclusions, to which mere experiments cannot reach, although they may serve, so to speak, to guide. With regard to the use of the study of Mechanics, theoretically considered, I would beg to call your attention to the following. The more we study the various phenomena of Nature the more we discover-the more strongly are we driven to the belief, that the vast diversity of effects, which we daily witness, result from the motions of particles of matter; brought about by the agency of certain forces with which the Creator of all things has purposely endowed them. The operations of Chemistry—the action of Organic and Inorganic Matters on each other-the phenomena of Electricity-of Light-of the Celestial Bodies--and of Animal and Vegetable Life, all tend to the confirmation of such a belief. It is stated, by those who are the best qualified to give an opinion on these matters, that "The progress of science begins clearly to indicate, that the whole class of electrical facts will one day be included in some higher generalization than either of those by which they are at present grouped together. Attempts have

been made, and not altogether without success, to connect, in one general theory, all attractive and repulsive forces, not excepting the universal force of gravity itself." I do not know a single phenomenon of Nature, to whatever branch of natural science it may belong, which is not resolvable in the end into motion. The prevailing theories, in every department of Natural Philosophy, have their foundation in the motions of particles, produced by the agency of attractive and repulsive forces. The right understanding, then, of these theories requires a previous acquaintance with Mechanics. But when I feel that I am addressing the young and ardent in the pursuit of knowledge; those, some of whom may be inclined, hereafter, to take a higher ground in the study; some who, perhaps, hope to advance our knowledge of the operations of Nature; some who hope, it may be, with beating hearts, one day to rank amongst the distinguished philosophers of the time; to those I would say, you can only expect to succeed by laying such a sure foundation in mechanical science as will enable you to surmount the difficulties, which must inevitably obstruct your path. It is in investigations of this nature that is best seen the use of mathematical attainments. Indeed, I think I may say that the main use of the study of the Mathematics is to advance physical science, and our knowledge of the machinery of Nature. "For all the difficulty of philosophy seems to consist in this, from the phenomena of motions to investigate the forces of Nature, and then from these forces to demonstrate the other phenomena ;" until we can show, as it has been beautifully remarked by a popular poet,

"That very law which moulds a tear,

And bids it trickle from its source,

That law preserves the earth a sphere,

And guides the planets in their course."

In Newton's preface to the Principia occurs the following remarkable passage. After speaking of the motions of the planets, the comets, the moon, and the sun, he continues, "I

wish we could derive the rest of the phenomena of Nature by the same kind of reasoning from mechanical principles. For I am induced, by many reasons, to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown, philosophers have hitherto attempted the search of Nature in vain." Now modern science is gradually unfolding these unknown forces, as Newton calls them. Indeed, another Newton is now wanted, whose comprehensive grasp of mind and perfect familiarity with Mechanics shall enable him to string together, by a general theory, like beads upon a string, the various facts with which observation and experimental research have made us acquainted.

II. In the application of Natural Philosophy to practical purposes, no branch, perhaps, after Mechanics, is of more importance than Pneumatics. It treats of the pressure of

Elastic Fluids; viz. of the pressure of Gases and Vapours. That most important of all machines the steam engine, is essentially a pneumatic machine. Were the study of this branch of science, therefore, of no other use than to enable us rightly to understand the action of the steam engine, it would on that account alone be invaluable. A multitude, however, of other most useful machines can be explained and understood, only by a previous acquaintance with the properties of elastic fluids. A variety of interesting and beautiful natural phenomena fall for explanation under this branch of physical science. In my opinion, there is no department of Natural Philosophy more generally interesting; more practically useful; or which abounds with more elegant and convincing experiments. As my time, however, is limited, I shall not dwell upon this subject, but proceed to make some observations on Acoustics.

III. The science of Acoustics is practically important, since the structure and action of all musical instruments can

only be clearly comprehended by those who possess a competent knowledge of this branch of Natural Philosophy. "The doctrine of sound," observes Sir John Leslie, "is unquestionably one of the most subtile and abstruse in the whole range of physical science. It has given occasion, in recent times, to much controversy and discussion, and has eventually called forth all the mighty resources of a refined and elaborate calculus. Yet an evident obscurity still remains to cloud the subject. The discrepancies between theory and observation have been made entirely to disappear from Astronomy, which has at last attained a degree of perfection befitting the sublimity of the science. But some latent suspicions pervade the structure of Acoustics, sufficient to disturb that feeling of confidence which is calculated to invigorate our pursuits." The fundamental principles of Acoustics will be found, however, to be susceptible of varied and beautiful experimental illustration, which it will be my endeavour to exhibit in those lectures that I shall deliver upon this interesting subject. The general student will find in those lectures explanations of the theory of music and of musical instruments; of the organs of speech and hearing; as well as of a variety of singular and beautiful natural phenomena. The more advanced student will find in this, (perhaps more than in any other branch of physical science, excepting the analogous phenomena of light,) abundant exercise for his mathematical abilities. The study of the vibration of bodies, and of acoustic curves will be found to present so many points of resemblance between Acoustical and Optical phenomena, that the careful investigation of the doctrine of sound, will prepare the student of Nature advantageously for the undulatory theory of light.

IV. Heat must always take a high rank amongst the experimental sciences. In practice few branches are more useful. A knowledge of the properties of heat; its conduction by, its radiation from, and its transmission through various bodies, is required to the proper working of the steam

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