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times -- wi 30 * , ° oe THE LAWS OF MAGNETISN. SUGGESTIONS TO THE STUDENT AS TO METHOD OF STUDYING MAGNETISM. : This lesson is intended to_ be . self-explana- tory; help from a teacher being unnecessary. The student should first read over several due thought and deliberation Part T of the "Laws of Magnetism' (Magnetism by Theory), before taking up the experimental study of the science, or the practice of its art, which is contained in Part II, By following this method closely the student will obtain a theoretical knowledge of the fundamental prin- ciples of the science by simply reading the lesson over a few times, and weighing in the mind its laws, rules and principles, thus form- ing a true and satisfactory solution tending to explain and clear up _ the seemingly per- plexing laws that constitute the essential part or foundation of any science. : This is the correct course for the student to pursue in obtaining the necessary axis or groundwork, so essential to the thorough and comprehensive understanding of the study. The law governing the principle of, the ex- periment to be performed is first explained, 'science distinguished from the art; and .then comes the experiment itself, or the theory put to practice. : think; and, therefore, when he gives the state: --ment of a principle, he has the knowledge of - actual experience behind that statement. Such a. knowledge will prove helpful to the student in the practical solution of all theo- retical problems thus learned, as* well as by their experimental demonstration. : It is the theoretical part of my study that the beginner needs first. Practice will avail little or nothing unless it be founded upon correct theoretical principles, and these ciples understood by the student. Theory is founded on principles which been established on independent evidence. The the rules of an art, as distinguished from the practice. Practice is the capability of reducing know- ledge or theories to actual use or experience, not visionary; Opposed to theory. Taught or instructed by practice, use, or experience; hav- ing derived skill from actual work or experi- have "ence. - ject up in the experimental knowledge by the student ples. Theory is of little account unless closely as- sociated with practice. Much, of course, can be accomplished by practice alone, but more when accompanied by theory. One is the es- sential of the other, and without the two to- gether one can never hope to be thoroughly proficient in acquiring a full and correct know- ledge of any special branch of study; and with- out first clearly comprehending the laws upon which a theory 'is based, it cannot be. per- formed in practice with any degree of certainty or satisfaction. 4 i All theories, when possible, should be put. into practice. _ There will probably be many laws and a ciples in the theoretical study of magnetism that will at first tend to puzzle the student in reaching a satisfactory explanation: of same. Should this at' any time occur, after giving it careful thought and reflection, either throw it from the mind entirely for the time being and take up another subject that will gradually lead to the one just dropped, or take the same.sub- r study of the science, By experiment, in nine cases out of ten, a solution will be reached where the same laws and principles were meaningless theoreti- cally. This is likewise true of theory,. and the student in many cases will be able to grasp a meaning theoretically, even if he does not actually perform the experiment for him- self. One is a stepping stone to the other. Starting aright is of primary importance to the beginner in pursuing a course of study, and much depends on this point of elementary knowledge in the attainment or accomplishment of the object sought, i, e., a full and complete of the elementary facts and laws of the art he is studying. Familiarity with the rudimentary truths of the study of such an art is the source from which all knowledge is derived. The above facts show the necessity of an elementary training in order to give the mind a harmonious development, and preparing it to acquire all kinds of knowledge. The processes of every art are based on prin- ciples, and these when formulated become its rules, and hence a complete knowledge of an art includes a knowledge of its guiding princi- These principles are of little, if any, value to the learner unless brought out one by one, and reached by an analysis of familiar The student must . prin- - TAE MARINE REVIEW By Clarence E. Long processes and by the study of the productions that embody them. ; No mistake in the elementary teaching is more absurd or futile, than. the attempt to learn an art by simply. learning a_ theoretical: knowledge of the principles and _ processes. The mastery of. an art involves. the acquisition of skill, and a knowledge of the art is chiefly valuable as a means to this' end. Theory without practice cannot impart skill, and hence cannot make an artist. The study of any branch of physical science increases one's power to master any other physical science. It is also a fact that the study of a branch of knowledge that trains several powers of the mind may increase its capacity to master other branches that appeal ~ to these powers. 5 Learn to think and to think correctly is an important factor in the study of any art. One does not learn to think by, mere thinking, but that he learns to think correctly by the think- ing under guidance. There are many guiding posts'in the lesson following so that the student will have every chance and opportunity of thinking correctly. : Learn to be observing;, train yourself to be observing by cultivating the mind in that di- - rection. Think for yourself, and reason for yourself; do not have, or expect, someone else to do it for you; and above all learn to rely upon yourself. These are necessary require- ments for the student to acquire for a firm basis on which to build. beneficial. and lasting knowledge. - Noes The student should make it a point to investi- gate the "whys and wherefores"--the causes and effects of the various laws and principles in- volved in the different subjects so that he may "intelligently understand. what he is doing and 4 is done. Never learn rules or laws parrot-fashion. Learn the principles, then, if possible, make your own rules. If you know why you are doing a certain thing you can al- ways give a reason; this reason then should be your rule. Such rules will be living and lasting rules, not easily forgotten. The student should not become discouraged if he is unable to grasp. the meaning of each law or principle at first sight. They are much simpler than they appear at first. Re- member that this planet on which we live was not made in one day. Go slow and begin at the beginning. Be sure to do everything thoroughly that is done. Always. keep in mind what you have learned in vour previous lesson, Magnet.--A body possessing that peculiar form of polarity found in nature in the load- stone; a body capable of exerting and being acted on by magnetic force. Every such body has at least two opposite points or poles, each of which attracts one pole and repels the other of another magnet. Poles that are all attracted or all repelled by the same _ pole (hence called like poles) repel each other; those affected opnositely by the same _ pole, called unlike poles, attract each other. A mag- net induces magnetism in other bodies capable of becoming magnets, especially iron or steel, and therefore. attracts them, but it exerts its peculiar action only upon bodies which have magnetic properties. The earth acts like an immense magnet, of which the respective poles are within the arctic and antarctic circles, and hence causes a suspended magnet to point in the direction of them, which is nearly north and south. The end that points north is, called either the north, north-seeking, positive or red pole; the other, the south, south-seeking, nega- tive, or blue pole. Magnets. are either natural, when like the loadstone they are found already magnetized, or artificial, when magnetism has been given to them by -placing them in the field of another magnet or in that caused by an electric current. They are permanent when the magnetism re- mains after they have been removed from the exciting field. Permanent magnets are those made of highly tempered steel, and practically why it _the 'only magnetic substances are soft iron, and some of its oxides. MAGNETISM BY THEORY. PART I, An exhaustive inquiry into this most important subject "must involve a whole book on it alone, whilst in these pages we can afford it but a few chapters. The stone is the natural magnet. SCIENTIFIC LAKE, NAVIGATION object of these notes is to make known a plain and simple method of determin- ing its effect on, the magnetic needle. It is also intended to show that a prac- tical knowledge 'of the law of magne- tism can be easily acquired by any mas- ter or pilot, and thence the theory of the deviation of the compass and compass adjustment, or still better, compass com- pensation. It is absolutely necessary to : i 1S ; e Jo G a Cc "a --_ Se 2a SS Os Ses Bae eee NORTH POLR |m SOUTH POLE OR 21> Oe a RED POLARTY & BLUE POLARTY a jo FIG, I--POLES AND EQUATOR (NEUTRAL LINE) OF A SIMPLE BAR MAGNET. have an understanding of the principal features of the theory since it is certain that anyone who attempts compass ad- justment by mere "rule of thumb" with- out first clearly comprehending the laws upon which it is based, can never hope to perform it satisfactorily. THE ORIGIN OF THE MAGNET. Before going further with this subject let us trace the origin of the magnet. The magnet was not an invention, but a discovery. Little is known of its origin though the Chinese claim the distinction of having -first discovered, both its -at- tractive and pointing properties. The ancients were aware that the loadstone attracted iron,. but were for ages, ignor- ant of its directing property. It was through the loadstone that the discovery of the magnet--was made, and upon it the laws of magnetism are based. Load- It is mined the same as oré of iron to which it is closely related. It is in all shapes 'and sizes and is found-in all parts of. the world, It was the natural magnet: that was first used as-the magnet of the com- pass. After this 'it was discovered that by rubbing the natural magnet on a piece of tempered steel, it too became magtietic and had alk the properties of the natural magnet; that is, two magnetic poles of opposite magnetism, or a north ard south pole of magnetism. The latter