the astonishing statement in the same article that most of these so-called gravel implements of Europe are doubtless the rejects of manufacture," pre-historic archæologists, and especially those of Europe, will draw their own inferences as to the qualifications for pronouncing an ex cathedra decision of the man who made the statement (Science, Nov. 25, 1892) that "there is not in the museums of Europe or America a single piece of flaked stone found in place in the gravels of America and satisfactorily verified that can with absolute safety be classified as an implement at all." I have had occasion elsewhere to refer to Mr. Holmes's fondness for making startling assertions, instancing his statement about the Indians, in the same article in Science, that their “quarrying was accomplished mainly by the aid of stone, wood and bone utensils, aided in some cases perhaps by fire. With these simple means the solid beds of rock were penetrated to depths often reaching twenty-five feet." The readers of Science have lately had an opportunity of observing also that Mr. Holmes "strongly deprecates personalities in scientific discussion." HENRY W. HAYNES. Boston, March 30. BOOK-REVIEWS. The History and Theory of Money. By SIDNEY SHERWOOD. Philadelphia, J. B. Lippincott Co. $2. THIS book contains twelve lectures delivered in the university extension course at Philadelphia last year before a company of bankers and others interested in the subject of finance Half the lectures are professedly historical and the other half theoretical; but the historical element is really predominant throughout them all. This seems to us a mistake, for the history of money cannot be properly understood nor appreciated without a previous acquaintance with the theory, and in these lectures the theory is not stated with anything like the clearness and fulness which A Tonic the subject demands. However, it was expected that the attendants on the lectures would read and study for themselves during the progress of the course, the books recommended for their use being named in this volume; and such reading would supplement the instruction given in the lectures. Mr. Sherwood, who is attached to the Wharton School of Finance in the University of Pennsylvania, shows a thorough familiarity with his subject, and, what is quite as important, he has no hobbies to ride, and is not prone to extreme or one-sided views. He begins by showing what money is for, what purposes it fulfils in the world's economy, and then proceeds to treat of the different kinds of money in use, with remarks on coinage, on the history of the precious metals, and on government notes and bank notes, with brief discussions of some of the many economic questions which those subjects involve. The lectures are expressed in a plain and straightforward style, which the hearers could readily understand, and they were evidently enjoyed by those who listened to them. For our part, however, we have found the discussions at the end of each lecture, and which are here reported in brief, the most interesting part of the book as well as the most suggestive. There were many persons in the audience well equipped with both theoretical and practical knowledge of the subject, and their discussions with Mr. Sherwood and with one another called up many points that were not touched upon in the lectures, and presented various and sometimes conflicting views. Among the debaters was a lady of socialistic proclivities, whose remarks and questions added variety and piquancy to the scene, though she did not appear to have many sympathizers. On the whole, though it cannot be regarded as an adequate scientific treatisen money, this book will certainly have an interest for all who care for its subject. AMONG THE PUBLISHERS. J. B. LIPPINCOTT COMPANY announce as in preparation "Vagaries of Sanitary Science," by F. L. Dibble, M.D. For Brain-Workers, the Weak and to marine calibre, also land and fresh Debilitated. Horsford's Acid Phosphate is without exception the Best Remedy for relieving Mental and Nervous Exhaustion; and where the system has become debilitated by disease, it acts as a general tonic and vitalizer, affording sustenance to both brain and body. For sale or exchange.-One good long range Rem water, and shells. Want shells, Safety, camera or printing press. A. H. Boies, Hudson, Mich. Fine collection of microscopic slides for sale, or would exchange for first-class pneumatic bicycle. J. E. Whitney, Box 549, Rochester, N. Y. WANTED-Second-hand copy Tryon's Systematic H. L. Osborn, Hamline University, St. Paul, Minn. A COMPETENT TEACHER of botany in college or university is open to engagement. Address L., Box 86, Rochester, Mich. For sale-A Zentmayer new model U. S. Army Hospital monocular stand. Price $110, will sell for $75. Address H. C. Wells, No. 151 Broadway, New York. American Journal of Science (1870-1898) handsomely cats have lived? I have one twenty years old. co Address G. H. Williams, 803 Cathedral Street, For sale, or for exchange for books on medi-Wor's Comparative Embryology, Claus & For sale-A complete set of the third series of the cine or surgery, new editions only, a large geo- logical library, containing nearly all the State to For exchange.-Slides of Indian Territory Loup Dr. J. C. Wilson, Philadelphia, Pa., For exchange.-Will exchange an "Ideal" Misays: "I have used it as a general tonic, croscope of R and J. Beck, London, 2 eye pieces 3 objectives, 3 inch, 1 inch, 1-6 inch; bull's eye con and in particular in the debility and denser on stand, substage condenser, mechanica stage, etc., for any of the leading makes of type dyspepsia of overworked men, with sat-writers. Particulars by mail. DELOS FALL, Albion College, Albion, Mich. isfactory results." Descriptive pamphlet free. For sale or exchange. I have a few copies of my translation of "Strasburger's Manual of Vegetable Histology, 1887," now out of print, which I will send AN any one inform me as to the age to which Edward D. Webb, 132 W. Eighty-first St., New York. ANTED Second-hand. Foster's Physiology, Sedgwick's Zoology, Flower's Osteology of Mameditions and prices asked and address Richard malla, Vine's Physiology of Plants. Please state Lees Brampton, Ontario, Canada sale will please address the undersigned, stating WANTED.-American Journal of Conchology, seven volumes. Parties having these for condition and price. R. Ellsworth Call, Louisville, Ky. GRADUATE ENGINEER will give instruction A evenings in geometry, trigonometry and surveying, mechanics, physics, mechanical drawing and general engineering construction. Five years experience in field and editorial work on engineering journal. References furnished. C. S. H., 102 Tribune Building, New York. post-paid for $8 or for one dozen good slides illus-WAN Rumford Chemical Works. Providence, R. I. trating plant or animal structure. Address A. B. Beware of Substitutes and Imitations. Hervey, St. Lawrence University, Canton, N. Y. For sale or exchange.-A private cabinet of about 200 species of fossils, well distributed geologically and geographically, Silurian, about 40; Devonian, about 50; Carboniferous, about 80; others, about 80. Frank S. Aby, State University, Iowa City, Ia. Paris and London Costumes, MARY TAYLOR BISSELL. 12°. 75 cents. N. D. C. HODGES, Publisher, found which show that when the conductor is dissipated the build NEW COLORINGS AND NEW MATERIALS. THE MODERN MALADY; or, Suf- ing is not injured to the extent ferers from 'Nerves.' An introduction to public consideration, from a non-medical point of view, of a con explained (for many of these see volumes of Philosophical Transactions at the time when light dition of ill-health which is increasingly ning was attracting the attention prevalent in all ranks of society. In the first part of this work the author dwells on of the Royal Society), but not the errors in our mode of treating Neuras thenia, consequent on the wide ignorance of an exception is yet known, al- ond part, attention is drawn to the principal though this query has been pub- 95 MILK ST., BOSTON, MASS. thought suitable to this most painful and try This Company owns the Letters - Patent No. 186,787, granted to Alexander Graham Bell, January 30th, 1877, the scope of which has been defined by the Supreme Court of the United States in the following terms: "The patent itself is for the mechanical ing disease. By CYRIL BENNETT. 12°, 184 pp., $1.50. structure of an electric telephone to be used N. D. C. HODGES, 874 Broadway, N. Y. to produce the electrical action on which the first patent rests. The third claim is for the use in such instruments of a diaphragm, made of a plate of iron or steel, or other material capable of inductive action; the fifth, of a permanent magnet constructed as de scribed with a coil upon the end or ends POPULAR MANUAL OF VISIBLE SPEECH AND For use in Colleges and Normal Schools. Price 50 cents tricians. First inserted June 19, 1891. No response to date. N. D. C. HODGES, 874 BROADWAY, N. Y. 10% DISCOUNT. We will allow the above discount to any subscriber to Science who will send us an each at its full price. order for periodicals exceeding $10, counting nearest the plate; the sixth, of a sounding N. D. C. HODGES, 874 Broadway, N. v. N. D. C. HODGES, 874 Broadway, N. Y. box as described; the seventh, of a speaking or hearing tube as described for conveying the sounds; and the eighth, of a permanent magnet and plate combined. The claim is not for these several things in and of themselves, but for an electric telephone in the construction of which these things or any of them are used." This Company also owns Letters-Patent No. 463,569, granted to Emile Berliner, November 17, 1891, for a combined Telegraph and Telephone, and controls Letters-Patent No. 474,231, granted to Thomas A. Edison, May 3, 1892, for a Speaking Telegraph, which cover fundamental inventions and embrace all forms of microphone transmitters and of carbon telephones. "BUSY FOLKS' GYMNASIUM." A few minutes' daily exercise our fascinating apparatus clears the brain, tones up the body, develops weak parts. Our cabinet contains chest-weights, rowing-weights, lifting-weights, clubs and dumb bells, adjustable for old and young. It is the only complete exercising outfit in the world suitable for use in living rooms. All prices. You can order on approval. Chest machine separate, $4.50 and up. good for Round Shoulders. Educated agents wanted. PHYSI GEO. L. ENGLISH & CO., Mineralogists, naming this paper. ་ Removed to 64 East 12th Street, New York. WHITNEY HOME GYMNASIUM CO., Box D., Rochester, N. Y. SINGLE COPIES, TEN CENTS. $3.50 PER YEAR, IN ADVANCE. BUSINESS OPPORTUNITY. There is an opening for a His Career at Harvard-His Travels-His Re- young man to open a New has ever been prepared, and this volume can be Taken as a whole no more useful life of Agassiz York office of the American warmly recommended to all who wish to gain familiarity with one whose name and fame will live always. The illustrations are excellent."-Boston Times. Lightning Protection Co., Mr. Holder has devoted himself rather to the operating under my patents. story of Agassiz's life and accomplishment than to an analysis of him as a scientist. He has made a thoroughly interesting volume, wholesome, helpful to all classes of renders."-Providence Journal. But little capital will be re 1. CHARLES DARWIN. His Life and Work. quired. N. D. C. HODGES, By CHARLES F. HOLDER. 12mo, illustrated, $1.50. "Mr. Holder is one of the American savants who have made Darwin and his system of philosophy a subject of profound study, and his book relating to him is one of the best that have been produced for 874 BROADWAY, NEW YORK popular use "-Philadelphia Bulletin. The author has given us a capital account of Darwin's voyages, adventures, and discoveries, indicating in broad outlines his theories and scientifle opinions, and not neglecting to throw into strong light the lovable personal character and individual traits of the great naturalist."-Christian Union. Notes on New Books, a quarterly bulletin, prospectus of the Story of the Nations and Knicker. bocker Nuggets sent on application, G. P. PUTNAM'S SONS, NEW YORK: 27 and 29 W. 23d Street. NEW METHOD OF PROTECTING BUILDINGS FROM LIGHTNING. SPARE THE ROD AND SPOIL THE HOUSE ! Lightning Destroys. Shall it be Your House or a Pound of Copper? PROTECTION FROM LIGHTNING. What is the Problem? IN seeking a means of protection from lightning-discharges, we have in view two objects, the one the prevention of damage to buildings, and the other the prevention of injury to life. In order to destroy a building in whole or in part, it is necessary that work should be done; that is, as physicists express Ir, energy is required. Just before the lightning-discharge takes place, the energy capable of doing the damage which we seek to preveut exists in the column of air extending from the cloud to the earth in some form that makes it capable of appearing as what we call electricity. We will therefore call it electrical energy. What this electrical energy is, it is not necessary for us to consider in this place; but that it exists there can be no doubt, as it manifests itself in the destruction of buildings. The problem that we have to deal with, therefore, is the conversion of this energy into some other form, and the accomplishment of this in such a way as shall result in the least injury to property and life. Why Have the Old Rods Failed? When lightning-rods were first proposed, the science of energetics was entirely undeveloped; that is to say, in the middle of the last century scientifle men had not come to recognize the fact that the different forms of energy — heat, electricity, mechanical power, etc.-were convertible one Into the other, and that each could produce just so much of each of the other forms, and no more. The doctrine of the conservation and correlation of energy was first clearly worked out in the early part of this century. There were, however, some facts known in regard to electricity a hundred and forty years ago; and among these were the attracting power of points for an electric spark, and the conducting power of metals. Lightning-rods were therefore introduced with the idea that the electricity existing in the lightning-discharge could be conveyed around the building which it was proposed to protect, and that the building would thus be saved. The question as to dissipation of the energy Involved was entirely ignored, naturally; and from that time to this, in spite of the best endeavors of those interested, lightning-rods constructed in accordance with Franklin's principle have not furnished satisfactory protection. The reason for this is apparent when it is considered that the electrical energy existing in the atmosphere Sefore the discharge, or, more exactly, in the column of dielectric from the cloud to the earth, above referred to, reaches its maximum value on the surface of the conductors that chance to be within the column of dielectric; so that the greatest display of energy will be on the surface of the very lightningrods that were meant to protect, and damage results, as so often proves to be the case. It will be understood, of course, that this display of energy on the surface of the old lightning-rods is aided by their being more or less Insulated from the earth, but in any event the very existence of such a mass of metal as an old lightning-rod can only tend to produce a disastrous dissipation of electrical energy upon its surface," to draw the lightning," as it is so commonly put. Is there a Better Means of Protection? Having cleared our minds, therefore, of any idea of conducting electricity, and keeping clearly in view the fact that in providing protection against lightning we must furnish some means by which the electrical energy may be harmlessly dissipated, the question arises, "Can an improved form be given to the rod, so that it shall ald in this dissipation?" LONDON: 24 Bedford St., Strand. USEFUL HAND-BOOKS. bets, for sign-writers, engravers, stone-cutters and The Ornamental Penman's Pocketbook of AlphaHoward Cromwell, 50 cts. draftsmen, 20 cts. A System of Easy Lettering, by Practical Electrics: A Universal Handybook on Every-day Electrical Matters, 135 pp., fully illustrated, 12mo, cloth. 75 cts. Notes on Design of Small Dynamo, by G. Halliday, 79 pp., with a number of plates to scale, 12mo, cloth, $1. The Phonograph and How to Construct It, by W. Gillett, 87 pp., 12 folding plates, 12mo, cloth. $2. SPON & CHAMBERLAIN, Publishers, 12 Cortlandt St., New York. Illustrated and descriptive cata| logues, 10 cts. As the electrical energy involved manifests itself on the surface of conductors, the Improved rod should be metallic; but, instead of making a large rod, suppose that we make it comparatively small in size, so that the total amount of metal running from the top of the house to some point & little below the foundations shall not exceed one pound. Suppose, again, that we introduce numerous Insulating joints in this rod. We shall then have a rod that experience shows will be readily destroyed-will be readily dissipated when a discharge takes place; and it will be evident, that, so far as the electrical energy is consumed in doing this, there will be the less to do other damage. The only point that remains to be proved as to the utility of such a rod is to show that the dissipation of such a conductor does not tend to injure other bodies in its immediate vicinity. On this point I can only say that I have found no case where such a conductor (for instance, a bell wire) has been dissipated, even If resting against a plastered wall, where there has been any material damage done to surrounding objects. Of course, it is readily understood that such an explosion cannot take place in a confined space without the rupture of the walls (the wire cannot be boarded over); but in every case that I have found recorded this dissipation takes place just as gunpowder burns when spread on a board. The objects against wolch the conductor rests may be stained, but they are not shattered, I would therefore make clear this distinction between the action of electrical energy when dissipated on the surface of a large conductor and when dissipated on the surface of a comparatively small or easily dissipated conductor. When dissipated on the surface of a large conductor, a conductor so strong as to resist the explosive effect, - damage results to objects around. When dissipated on the surface of a small conductor, the conductor goes, but the other objects around are saved A Typical Case of the Action of a Small Conductor. Franklin, in a letter to Collinson read before the London Royal Society, Dec. 18, 1755, describing the partial destruction by lightning of a church-tower at Newbury, Mass, wrote, "Near the bell was fixed an iron hammer to strike the hours; and from the tail of the hammer a wire went down through a small gimlet-hole in the floor that the bell stood upon, and through a second floor in like manner; then horizontally under and near the plastered ceiling of that second floor, till it came near a plastered wall; then down by the side of that wall to a clock, which stood about twenty feet below the bell. The wire was not bigger than a common knitting needle. The spire was split all to pieces by the lightning, and the parts flung in all directions over the square in which the church stood, so that nothing remained above the bell. The lightning passed between the hammer and the clock in the above-mentioned wire, without hurting either of the floors, or having any effect upon them (except making the gimlet-holes, through which the wire passed, a little bigger), and without hurting the plastered wall, or any part of the building, so far as the aforesaid wire and the pendulum-wire of the clock extended; which latter wire was about the thickness of a goose-quill. From the end of the pendulum, down quite to the ground, the building was exceedingly rent and damaged. . . . No part of the aforementioned long, small wire, between the clock and the hammer, could be found, except about two inches that hung to the tall of the hammer, and about as much that was fastened to the clock; the rest being exploded, aud its particles dissipated in smoke and air, as gunpowder is by common fire, and had only let a black smutty track on the plastering, three or four inches broad, darkest the middle, and fainter towards the edges, all along the ceiling, under which it passed, and down the wall." One hundred feet of the Hodges Patent Lightning Dispeller (made under patents of N. D. C. Hodges, Editor of Science) will be mailed, postpaid, to any address, on receipt of five dollars ($5). Correspondence solicited. Agents wanted. AMERICAN LIGHTNING PROTECTION CO., 874 Broadway, New York City. RACES AND PEOPLES. By DANIEL G. BRINTON, M.D. "The book is good, thoroughly good, and will long remain the best accessible elementary ethnography in our language."-The Christian Union. "We strongly recommend Dr. Brinton's Races and Peoples' to both beginners and scholars. We are not aware of any other recent work on the science of which it treats in the English language." -Asiatic Quarterly. "His book is an excellent one, and we can heartily recommend it as an introductory manual of ethnology."-The Monist. "A useful and really interesting work, which deserves to be widely read and studied both in Europe and America."-Brighton (Eng.) Herald. "This volume is most stimulating. It is written with great clearness, so that anybody can understand, and while in some ways, perforce, superficial, grasps very well the complete field of humanity."The New York Times. "Dr. Brinton invests his scientific illustrations and measurements with an indescribable charm of narration, so that 'Races and Peoples, avowedly a record of discovered facts, is in reality a strong stimulant to the imagination."-Philadelphia Public Ledger. "The work is indispensable to the student who requires an intelligent guide to a course of ethnographic reading."-Philadelphia Times. Price, postpaid, $1.75. N. D. C. HODGES, 874 BROADWAY, NEW YORK. "IS SIMPLIFIED A Symposium by Prof. F. A. March, President of the American Philological Society; Hon. A. R. Spofford. Librarian of Congress; Dr. Alexander Melville Bell, author of "World English "; Dr. W. T. Harris, Commissioner of Education; Prof. W. B. Powell, Superintendent of Public Schools; Prof. Benjamin E. Smith, Editor of the Century Dictionary; Mr. J. C. Pilling, Bibliographer; Prof. C. P. G. Scott, Editor of Worcester's Dictionary; Prof. W. B. Owen, of Lafayette College; Maj. J. W. Powell, Director of Bureau of Ethnology; Prof. W. D. Whitney, of Yale College: Dr. John M. Gregory, of the Civil Service Commission. It will comprise about one hundred pages of the April number of THE AMERICAN ANTHROPOL OGIST. Subscription price of the Quarterly, $3.00 per annum. The American Anthropologist, BRENTANO'S, Publishers, Importers, Booksellers. We make a specialty of technical works in all branches of science, and in all languages. Subscriptions taken for all American and foreign scientific periodicals. Our Paris and London branches enable us to import at shortest notice and lowest prices. REPORTS OF SCIENTIFIC SOCIETIES, MONOGRAPHS, GOVERNMENT REPORTS, etc. Correspondence solicited. Sportsmen and ornithologists wil pe interested in tant suggestions; and it is hoped that this feature of the book will recommend it to collectors of Ameri cana. It is hoped that the volume will serve as a guide to the Labrador coast for the use of travellers, yachtsmen, sportsmen, artists, and naturalists, as from us. A. ROCHESTER FELLOW. With thirty-two Illustrations and a Map. 12°. $1.50. "This is a sprightly narrative of personal incident. The book will be a pleasant reminder to many of rough experiences on a frontier which is rapidly receding."-Boston Transcript. "The picture of our desolate North-western territory twenty-five years ago, in contrast with its civilized aspect to-day, and the pleasant features of the writer's style, constitute the claims of his little book to present attention."-The Dial. N. D. C. HODGES, 874 Broadway, New York, N. Y. per week, to Agents, Ludles or Gentlemen, using or selling "Old Rellable Plater." Only practical way to re jate rasty aud worn knives, forks, spas, ete quickly done by dipping in melted metal. No experience, pulishing or machinery. Thick plate & Ev operation; lasts 5 to 10 years, ane doish when taken from the plater. Every family has plating to de. Plater is readily. Protis largs. W. . Harrison & Co., Columbus, O. $25 to $50 HALSTED'S ELEMENTS OF GEOMETRY. Fifth ed., postpaid, $1.75. HALSTED'S ELEMENTARY SYNTHETIC GEOMETRY, Post- HALSTED'S LOBATSCHEWSKY'S NON-EUCLIDEAN GEOM- BRENTANO'S, Union Square, New York, HALSTED'S BOLYAI'S SCIENCE ABSOLUTE OF SPACE. We Newspaper Clippings. 25,000 in Stock. What do you want? Let us know. can supply you. The Clemens News HALSTED'S GEOMETRY OF POSITION (Rigidly non quantitative). To appear shortly. Mathematics, University of Texas, Austin, Texas. Address GEORGE BRUCE HALSTED, Professor of well as those interested in geographical and histori- Agency, Box 2329, San Francisco, Cal. GERMANIA A monthly magazine for the study cal studies. German and literature, is highly recommended by college professors and the press as "the best effort yet made to assist the student of German, and to interest him in his pursuit. Its BEGINNERS' CORNER furnishes every year a complete and interesting course in German grammar. $2 a year. Single copies 20 cents. P. O. Box 151, Manchester, N. H. SCIENCE NEW YORK, APRIL 21, 1893. LABORATORY INSTRUCTION IN PHYSICS. BY D. W. HERING, UNIVERSITY OF THE CITY OF NEW YORK. THERE are various practices, and seemingly but two clearly defined methods of teaching physics in college laboratories. The first method, which may be called the progressive one, treats the general subject of physics by going through its various divisions successively, until the whole ground has been covered, whether thoroughly or superficially. For students who have had no preliminary training in physics, this method is the only practicable one if they are to begin their study in the laboratory. The other may be called the method of analysis. It assumes that the pupil has received a fair course of instruction in the principles of the science before he enters upon laboratory work. Then it is a matter of indifference whether his first exercise is one in optics. or in electricity; in radiation, or in specific gravities. He will examine a body of any sort with reference to its various properties, taking account of as many as he can, which in some instances may embrace nearly the whole range of physics. This method then does not present the different features of physics so much as the physical features of different things. At first sight it would appear as if the method that is pursued for the direct purpose of learning the science would be the one best fitted to give an acquaintance with it, and perhaps this would be true if sufficient time could be given to it to deal with the various branches of physics with tolerable thoroughness, but laboratory work by an untrained pupil is slow at best, and time is limited. It is important, therefore, to follow the plan that will give good results without loss of time. If physics as a science were distinctly progressive in its nature, one step being essential to a comprehension of the next, and therefore of necessity a preliminary to it, there could be no question as to the best order of proceeding in teaching or in learning the subject. There would still be room for question as to how much should be done by the teacher in experimental illustration with discussions, before putting the pupil to experimenting on his own account, but the order of dealing with the subject in any case would be determined beforehand. But it is thus progressive to only a limited degree. Except for the principles of mechanics, which permeate the entire science, physics, in all its diversity, may be dealt with regardless of the order in which the subjects are taken up And this exception is not always recognized. Among recent standard text-books which are meant to be especially adapted to laboratory practice, but which mean to omit none of the elementary principles of physics, there is every variety in arrangement of topics. One begins with specific gravity and air pressure, follows with dynamical principles, and presents light as the final subject. Another begins with magnetism, introduces the last third of the work by dynamics, and closes with sound. Still another begins with properties of matter and dynamics and ends with light; while a fourth begins with the mechanical powers and closes with magnetism and electricity. Even the special divisions, as electricity, for example, can scarcely be said to be developed from one principle that necessarily comes first, to another that can be reached only at the end of a well-defined series. Some classification of topics can always be made, but the tendency to-day is to diminish rather than increase the number of classes. Considerations of intrinsic difficulty, or length of time that can be given without interruption, or the season of the year when sunny days may be expected, or other special points may lead to a preference as to the order of subjects, but there is little in the nature of the subjects themselves to determine it. ures. The status of the student when he is to enter upon the work which this paper is to discuss, will depend upon the manner in which he obtained his first training in physics. He may have acquired his early knowledge by experimentation from the beginning, or he may have been taught from descriptive text-books supplemented by experimental lectures from the teacher, or he may have had a combination of both. In the first case, he had to find out principles and laws as well as (to him) disconnected facts by his own experimentation; in the second, he has been made acquainted with the leading laws and properties and perhaps has had some opportunity to verify and apply them. Whether an attempt to learn physics from the beginning by practice is profitable or advisable has been much discussed, and it is outside of our purpose to enter upon that question. It is a plan that has grown in favor greatly of late, and has been insisted upon by Harvard College, as a preparation for those who are to pursue the subject in college. Let us suppose the pupil to have acquired a general, though elementary, acquaintance with the principles of the science, that he has reached the standard of at least a well-prepared college junior. For this he has probably been called upon to cover the whole range of the subject whether by experiment, or by recitations and experimental lectThe advocates of the two methods of preparation will find points to offset one another in the results attained. The experimental student will have acquired his knowledge in a very valuable way, by objective study, by the inductive method. He will have learned to do by doing." This has become a favorite idea with educators in almost every branch of learning, and its advantages are undeniable in most lines of work, but they are not equally great or equally obvious in all branches or at all stages. It is a most effective way so far as it goes, but in physics the experiments concerning any one point, or involving any law, will have been so small in number under the best opportunities, that the student must infer the law from instances altogether too few and too little varied, to justify an inference. Potent as the inductive method has been in science, its demonstrations are never incontestable, they never rise above a moral certainty, and do not even approach it, if the instances upon which the conclusions are based are not numerous, or else very accurate. The student will in reality have done nothing more than illustrate a point, doing in a crude way what the lecturer before a large class does in a better way. Still the experiment and its results will impress themselves upon him because he did the work himself. In this he will have the advantage of the lecture-taught student. The knowledge of the latter, however, is likely to be more correct as to principles. On the whole, the two classes may be said to approach the higher laboratory practice about equally well equipped: the former better prepared for manipulation with perhaps less readiness to appreciate the science; the latter better prepared to discriminate as to principles, but less expert in determining them. Didactic and experimental instruction are now so well combined in some secondary schools as to make their work superior to that offered in many colleges. Having been fairly well taught by any method, we may suppose the student ready for practical work somewhat more advanced than is to be had in secondary schools, or even in the general course of physics in an average American college. What plan shall be followed in his laboratory work? Presumably that plan is best which is best fitted to accomplish its purpose. What is the purpose of his work? Usually not independent research or original investigation. Work of that class is generally undertaken only by graduates or special students, who are not obliged to accomplish a definite amount in a given time. The higher laboratory work of the college undergraduate is for the purpose of making him practically familiar with physical laws, not in one particular |