No branch of knowledge is more interesting or useful than that which teaches the physical constitution of the world in which we live, the appearances by which we are surrounded, and the laws which govern them. It cannot, however, be denied, that this subject has been greatly neglected, and that many educated men are as ignorant of the cause and influence of natural phenomena as though they had no interest in the provisions established for the support of animated being. This ignorance may be in part traced to erroneous systems of education; but it is also in some degree owing to a false estimate of the difficulties to be overcome in acquiring scientific knowledge, and an inadequate conception of its importance. It may not, therefore, be inconsistent with the character of this work, that we should present the reader with a few personal and relative motives to an acquaintance with the appearances of the material world, and the causes from which they flow; or, in other words, with the physical sciences.

Physical science, in its widest acceptation, embraces the investigation of matter in all its conditions and combinations. The entire material world comes under its cognizance. It not only considers the phenomena by which we are assured

of existence, but determines the properties of matter under all its forms, and the mutual influence which different species of matter, having various subordinate properties, exert upon each other. It embraces a knowledge of the laws of combination and form, the peculiarities of each element in itself, and in its union with others; and attempts to reveal the secret processes by which the universe itself is regulated.

Such a subject, however, would be far too extensive for the mightiest human intellect, and we are compelled to form certain artificial divisions, that, by the united efforts of many individuals, we may advance to some knowledge of the universe itself. The consideration of material existence has in consequence been assigned to three classes of philosophers, the natural historian, the chymist, and the experimental philosopher. To the first of these is appropriated the study of animals and vegetables, and the form and localities of mineral substances. The chymist investigates all those phenomena which alter the composition of bodies, and endeavours to determine the nature of the elementary substances which enter into their formation. To the experimental philosopher is assigned the investigation of the laws of matter, and the nature and cause of all those phenomena in which it suffers change without altering any of the essential properties of its composition. But, as these boundaries are artificial, they are often broken down, for the gradation from one branch of knowledge to another is in nature so perfect, that it would be difficult to form such definitions as might prevent the student of one department from encroaching on the territories of others.

But although we have thus divided physical science, and have appropriated only so small a part to the experimental philosopher, it is still necessary to arrange the objects of his pursuit, and hence we have the sciences of hydrodynamics, electricity, and others. One great advantage has resulted from this subdivision. Men of investigation have been able to give their exclusive attention to particular subjects, and have thus been encouraged to pursue their inquiries at a time when knowledge was obtained with much difficulty. We would not, however, insinuate, that those who devote themselves to one science, are better fitted for discovery than those who have taken a wider view of nature. But, in the infantine state of philosophical knowledge, it was necessary, much more than at present, that there should be those who

could give their undivided attention to the accumulation of facts, leaving their combination and the deduction of general laws to others, who had either more of the inspiration of nature, or had taken a more extensive view of physical causes. It is not the collector of flowers, or of minerals, who can give the character of a country, and theorize on the problematic causes from which it originated, but the man who has traced the connexions of its parts, and from an eminence surveyed its outline, and marked its features. And he who in the general pursuit of knowledge has cultivated that spirit of generalization which can alone enable him to perceive the relations of different phenomena, will be best able to determine the character and influence of the immutable laws of nature.

It may be here necessary to remark, that in the study of nature, all preconceived opinions must be renounced; and the mind must ever be in a waiting attitude, ready to receive the evidence of phenomena, whether they contradict or support the theories which have been adopted.

We can conceive it possible that an individual should have so entirely devoted himself to other studies, as to be ignorant of every discovery of modern chymistry. Such an individual would consider water as an elementary substance, and, were we to speak of its decomposition, a feeling of incredulity would certainly rise in his mind. But, let him proceed to the investigation, and with a few plates of copper and zinc, this apparently elementary body will be decomposed, and the two gases of which it is constituted may be collected in separate tubes. One of these, he is informed, is oxygen, which is a component part of air, and the supporter of combustion; the other, hydrogen. When combined in the gaseous state, they form a most explosive compound; and, in proof of this fact, they are placed in the same tube, and ignited. But this last experiment resolves them again into the liquid state, and drops of water are observed around the tube. What must be the result of such experiments upon the mind of the man who is thus suddenly driven from an opinion that he had received upon the sanction of all the ancient philosophers! This, however, is but a solitary instance of what has continually occurred, and we are thus admonished to renounce the influence of all preconceived opinions in philosophical inquiries, and to give every phenomenon its true estimate in the determination of a cause.

But while the student carefully avoids the interference of his opinions with the evidence deduced from phenomena, he must at the same time carefully guard his mind against those deceptions which may be practised on him by his senses. The senses are not always to be trusted, for they frequently deceive us when we most depend on their evidence ; and this statement does not in any degree reflect upon the wisdom which was exerted in the formation of man, for his Creator has supplied him with that condition of mind which is amply sufficient to compensate for the inaccuracy with which those organs may convey an impression of external appearances.

But it may be still asked, what advantages are to be derived from the study of the physical sciences? and are they proportional to the labour which must be expended, and the mental discipline that must be suffered? These questions will be best answered by the mention of those results which ought to follow the investigation. We do not profess to teach the physical sciences, systematically, in this volume, but to explain the nature and cause of some of the most remarkable terrestrial and celestial phenomena, hoping to excite in the mind of the student an anxiety for a more extensive acquaintance with the sciences in general. It will not, therefore, be inappropriate to direct his attention to a consideration of those advantages which he may derive and confer upon society, by the study of this important branch of knowledge.

The personal advantages to be derived from the cultivation of natural philosophy, are chiefly mental. There are men who esteem themselves philosophers, and act as if this sentiment were highly enthusiastic and absurd. To what serviceable result can this or that study be applied? is the question which they are incessantly asking: by which they mean to inquire, how much money can be made of it. They are governed by the "auri sacra fames," and it for ever forbids their acquisition of the advantages in question. The best pleasures of life are but the flowers which beguile a laborious journey; and whatever may be the character of those we choose, they are usually obtained with difficulty. Those who select them from the paths of philosophy may receive titles of distinction, which, however, will not be conferred to encourage the pursuit, but to honour the title. The man who

devotes himself to the advancement of science, must seek his remuneration in the influence which it will exert on his own mind; and although he may be unrewarded by his contemporaries, he will possess many resources suited to sustain his independent energy under circumstances that ordinarily produce an injurious effect on the character.

nor.

Almost the first impression produced by the study of nature, is a conviction of the existence of a universal GoverAnd although we do not assert, or believe, that the Divine character is so evidently portrayed in material creation as in the inspired revelation, yet many principles of universal government may be deduced from the existence and action of those laws which regulate external phenomena. In every feature of nature, the philosopher may trace the evidence of mind, and his estimate of the wisdom displayed will be in proportion to the minuteness of his examination; and should he be deeply impressed with the universal and minute superintendence of a regulating Being, he will feel but little difficulty in committing himself to his government.

It has been asserted by some writers, that a close investigation of nature tends to cultivate or produce atheism. The habit which is acquired of tracing effects to their origin, leads, it is imagined, to a satisfaction with secondary causes, and induces the philosopher to close his investigations when on the verge of the noblest results; and investing physical operations with the attributes of Deity, to resolve all phenomena into the uncertain operations of chance, or to give the attribute of im mortality to all things. We might fairly deny this assertion, by adducing numerous instances in which the capability of most profound philosophical investigations has been united with the most exalted veneration of the Deity; and it may be questioned whether those who have denied the existence of a Superintending Power, derived their opinions from the examination of nature. But, judging of the statement by the reason given to support it, we need not hesitate to deny both the one and the other, for what can be more absurd than to believe, that a habit of tracing effects to their causes, prevents the mind from distinguishing between a primary and secondary agent?

A thousand individuals may pass over a beautifully varied country, and feel no other emotion than that arising from the influence of the scenery on the feelings. If they should be B