This is the fundamental experiment on which Clerk Maxwell's theory of light is based; but of late years many fresh facts and relations between electricity and light have been discovered, and at the present time they are tumbling in in great numbers.

clear to us-in fact, they could not have and for Clerk Maxwell more fully to been clear to him; but he seems to have develop, its most important consequences. felt a conviction that if he only tried [The principle of the experiment was long enough, and sent all kinds of rays then illustrated by the aid of a mechaniof light in all possible directions across cal model.] electric and magnetic fields in all sorts of media, he must ultimately hit upon something. Well, this is very nearly what he did. With a sublime patience and perseverance which remind one of the way Kepler hunted down guess after guess in a different field of research, Faraday combined electricity, or magnetism, and light in all manner of ways, and at last he was rewarded with a result. And a most out-of-the-way result it seemed. First, you have got to get a most powerful magnet and very strongly excite it; then you have to pierce its two poles with holes, in order that a beam of light may travel from one to the other along the lines of force; then, as ordinary light is no good, you must get a beam of plane polarized light and send it between the poles. But still no result is obtained until, finally, you interpose a piece of a rare and out-of-the-way material which Faraday had himself discovered and made, a kind of glass which contains borate of lead, and which is very heavy, or dense, and which must be perfectly annealed.

It was found by Faraday that many other transparent media besides heavy glass would show the phenomenon if placed between the poles, only in a less degree; and the very important observation that air itself exhibits the same phenomenon, though to an exceedingly small extent, has just been made by Kundt Röntgen in Germany.

Dr. Kerr, of Glasgow, has extended the result to opaque bodies, and has shown that if light be passed through magnetized iron its plane is rotated. The film of iron must be exceedingly thin, because of its opacity, and hence, though the intrinsic rotating power of iron is undoubtedly very great, the observed rotation is exceedingly small and difficult to observe; and it is only by very remarkable patience and care and ingenuity that Dr. Kerr has obtained his result. Mr. Fitzgerald, of Dublin, has examined the question mathematically, and has shown that Maxwell's theory would have enabled Dr. Kerr's result to be predicted.

And now, when all these arrangements are completed, what is seen is simply this, that if an analyzer is arranged to stop the light and make the field quite dark before the magnet is excited, thendirectly the battery is connected and the magnet called into action-a faint and Another requirement of the theory barely perceptible brightening of the is, that bodies which are transparent to field occurs; which will disappear if the light must be insulators or non-conductanalyzer be slightly rotated. [The ex- ors of electricity, and that conductors of periment was then shown.] Now, no electricity are necessarily opaque to wonder that no one understood this re- light. Simple observation amply consult. Faraday himself did not under- firms this; metals are the best conductstand it at all; he seems to have thought ors, and are the most opaque bodies that the magnetic lines of force were known. Insulators, such as glass and rendered luminous, or that the light was crystals, are transparent whenever they magnetized-in fact, he was in a fog, and had no idea of its real significance. Nor had any one. Continental philosophers experienced some difficulty and several failures before they were able to repeat the experiment. It was, in fact, discovered too soon, and before the scientific world was ready to receive it, and it was reserved for Sir William Thomson briefly, but very clearly, to point out,

are sufficiently homogeneous, and the very remarkable researches of Prof. Graham Bell in the last few months have shown that even ebonite, one of the most opaque insulators to ordinary vision, is certainly transparent to some kinds of radiation, and transparent to no small degree.

[The reason why transparent bodies must insulate, and why conductors must

be opaque, was here illustrated by mechanical models.]

than when it was in the dark. The light of a candle is sufficient, and instantaneously brings down the resistance to something like one-fifth of its original value.

I could show you these effects, but there is not much to see; it is an intensely interesting phenomenon, but its external manifestation is not striking-any more than Faraday's heavy glass experiment was.

This is the phenomenon which, as you know, has been utilized by Prof. Graham Bell in that most ingenious and striking invention, the photophone. By the kindness of Prof. Silvanus Thompson I have a few slides to show the principle of the invention, and Mr. Shelford Bidwell has been good enough to lend me his home-made photophone, which answers exceedingly well for short distances.

A further consequence of the theory is that the velocity of light in a transparent medium will be affected by its electrical strain constant; in other words, that its refractive index will bear some close but not yet quite ascertained relation to its specific inductive capacity. Experiment has partially confirmed this, but the confirmation is as yet very incomplete. But there are a number of results not predieted by theory, and whose connection with the theory is not clearly made out. We have the fact that light falling on the platinum electrode of a voltameter generates a current, first observed, I think, by Sir W. R. Grove-at any rate it is mentioned in his "Correlation of Forces extended by Becquerel and Robert Sa- I have now trespassed long enough bine to other substances, and now being upon your patience, but I must just alextended to fluorescent and other bodies lude to what may very likely be the by Prof. Minchin. And finally-for I next striking popular discovery, and that must be brief-we have the remarkable is the transmission of light by electriciaction of light on selenium. This fact ty; I mean the transmission of such was discovered accidentally by an assist- things as views and pictures by means ant in the laboratory of Mr. Willoughby of the electric wire. It has not yet Smith, who noticed that a piece of sele- been done, but it seems already theoretinium conducted electricity very much cally possible, and it may very soon be better when light was falling upon it practically possible.

SCIENCE TEACHING IN THE PUBLIC SCHOOLS.

From the Proceedings of the American Association for the Advancement of Science.*

REPORT OF COMMITTEE ON SCIENCE to a consideration of the subject. It was TEACHING IN THE PUBLIC SCHOOLS:

THE Committee appointed at the Saratoga meeting of the American Association on Science Teaching in the Public Schools, respectfully submit the preliminary Report.

The repeated appointment by this body, in successive years, of committees to look into the scientific education of the public schools, must be taken as showing that such an inquiry is regarded as both legitimate and important. Yet

the duties of such a committee have not

been defined by the Association, nor have any of our predecessors opened the way

The report of the Committee on Science Teaching in the Public Schools. The Committee consisted of

E. L. Youmans, A. R. Grote, J. W. Powell, N. S. Shaer and J. S. Newbery.

probably expected that we would furnish a digest of information from many quarters, as to what sciences are taught in the public schools, with what facilities, and to what extent; accompanied by such recommendations regarding the increase of scientific studies as the results might suggest. But our course has not proved to be so clear. We have been arrested at the outset by a question of the quality of the science teaching in these schools which demands the first consideration. There are certain radical deficiencies in current science teaching, the nature and extent of which must be understood before any measures of practical improvement can be intelligently taken up. We shall here confine ourselves to this preliminary inquiry.

The investigations has interest from of widely diffusing the results of rethe immense extent, and rapidly increas- search; but they recognized that the ing influence, of the American public interests of science are so vast, as to schools. There are now nearly one hun- be only efficiently promoted by division dred and fifty thousand of these schools, of labor. Under the operation of this supported at an annual expense of proba- principle it was made the distinctive purbly seventy or eighty million dollars. pose of the association to contribute to Maintained by state authority, they are the extension of original science by the firmly established in the respect and con- discovery of new scientific truth, leaving fidence of the community. Under the its dissemination to the schools, the press, influence of normal schools, teachers' and the various agencies of public eninstitutes, systematic superintendence, lightenment. Nor does your committee school boards, regulative legislation, and understand that it is now proposed to an extensive literature devoted specially depart from this policy; for the inquiry to education, they have become organ before us is really most pertinent to our ized into a system which is gradually special objects. It certainly cannot be a growing settled and unified in its meth- matter of indifference to this body, from ods. With unbounded means and un- its own point of view, how science is limited authority, these schools have dealt with in the great system of schools undertaken to form the mental habits of which. has undertaken the task of mouldthe great mass of the youth of this coun- ing the youthful mind of the country. try. They prescribe the subjects of We aim to advance science by the prostudy, the modes of study, and the ex- motion of original investigation, which tent and duration of studies for all the depends upon men prepared for the work. pupils that come under their charge. Do the schools of the nation, by their The sphere of their operations is, more- modes of scientific study, favor or hinder over, steadily extending. They are this object? Do they foster the early everywhere encroaching upon the prov- mental tendencies that lead to original ince of higher education, everywhere trenching upon private schools and diminishing the interest in home education.

It may be assumed that the time has fully come when this system must be measured by the standards of science, and approved or condemned by the degree of its conformity to what these standards require. Science has become in modern times the great agency of human amelioration, the triumphs of which are seen on every hand and felt in all experience. Grave subjects are brought successively under its renovating and reconstructive influence; and latest and most important among them is the subject of education. Our inquiry now is, how far the public-school system has availed itself of the valuable aid that science offers in the proper cultivation of the minds of the young.

The interest and necessity of such an investigation will hardly be denied; but there may be a query as to its relevancy to the appropriate work of this society. The making of science popular was not among the objects for which our association was formed. Not that its founders were unmindful of the importance

thought; or do they thwart and repress them? We have an undoubted concern in this matter, and it is, moreover, strictly identical with that of the community at large; for there can be no better test than this of the real character of a school system. When we ask whether a mode of teaching and a manner of study are calculated to awaken the spirit of inquiry, to cultivate the habit of investi gation, and rouse independent thought, our question goes to the root of all true education.

All sciences are the products of a method of thinking, and it is that method which concerns us when we propose to regard it as a means of mental cultivation. Science is an outgrowth of common knowledge, and the scientific method is but a development of the ordinary processes of thought that are employed by everybody. The common knowledge of people is imperfect because their observations are vague and loose, their reasoning hasty and careless, their minds warped by prejudice and deadened by credulity, and because they find it easier to invent fanciful explanations of things than to discover the real ones. For thousands of years the knowledge of nature

was rude and stationary because the said: "I will thank any person to show habits of thought were so defective. why it is expedient and beneficial in the But with a growing desire to understand community to make public provision for how the world around is constituted, teaching the elements of learning, and men improved their processes of think- not expedient or beneficial to make simiing. They began, and were compelled lar provision to aid the learner's progress to begin, by questioning accepted facts, toward the mastery of the most difficult and doubting current theories. The first branches of science and the choicest restep was one of self-assertion, implying finements of literature." Under the inthat degree of mental independence fluence of such considerations the rudiwhich led men to think for themselves. mentary studies rapidly developed into They learned to make their own observ- sources of study embracing a variety of ations and to trust them against au- subjects. This led to the systematizing thority. It was found, as a first and in- of instruction and the grading of schools, dispensable condition of gaining clear so that in nearly all the towns of the ideas, that the mind must be occupied United States the public schools have directly with the subject to be investi- been divided into primaries for the gated. In this way scientific inquiry at younger pupils and the grammar schools length grew into a method of forming for older pupils; while within twentyjudgments which was characterized by five years a third grade has arisen known the most vigilant and disciplined precau- as the high schools for the most advaneed tions against error. Of the mental pro- students.. In each division there are subcesses involved in research it is unneces- grades, and wherever improvements in sary here to speak; we are only con- public-school education are attempted, cerned to know that the scientific method the principle of gradation is fundamental. is simply a systematic exercise in truth- So essential is it considered, that no aid seeking, and is the only mode of using is granted from the Peabody fund exthe human mind when it is desired to attain the most accurate and perfect form of knowledge. The whole body of modern scientific truth, disclosing the order of nature and guiding the development of civilization, must be taken as an attestation of the validity of the scientific method of thought by which these results have been established. We here get rid of all cramping limitations. The are text-books upon all these branches, scientific method is applicable to all subjects whatever that involve constancy of relations, causes and effects, and conform to the operation of law. It is applicable wherever evidence is to be weighed, error got rid of, facts determined, and principles established. Our public schools, unhappily, make but little use of this method in the work of mental cultivation, and we shall find some explanation of this by referring to the way they grew

up.

The American public'school system originated in the theory that the State owes to every child the rudiments of a common education, or an elementary knowledge of reading, writing and arithmetic, as implements of after mental improvement. But it was early found difficult to separate the primary use of tools from the acquisition of knowledge. Mr. Everett

cept to graded schools. As regards the plan of studies adopted there was no guiding principle. All sorts of subjects, and these for all sorts of reasons were taken up, and among them the sciences which are now regular parts of public school duty. Classes are found in physics, chemistry, mineralogy, geology, physiology, botany and zoology. There

graded to the varying capacities of learners. Teachers prepare in them, and in many cases apparatus is provided, and there are lectures with experiments, spespecimens, maps and charts for illustrations.

The old ideal of a school is a place where knowledge is got from books by the help of teachers, and our public school system grew up in conformity with this ideal. The early effect of grading was to fix and consolidate imperfect methods. The sciences were assimilated to the old practice, and the science teaching falls short at just the points where it was inevitable that it should fall short. The methods of school teaching, and the habits of the teachers, had grown rigid under the regime of book-studies. As a consequence the science teaching in the public schools is

generally carried on by instruction. Through books and teachers the pupil is filled up with information in regard to science. Its facts and principles are explained as far as possible, and then left in the memory with his other school acquisitions. He learns the sciences much as he learns geography and history. Only in a few exceptional schools is he put to any direct mental work upon the subject-matter of science, or taught to think for himself.

fessed purpose of cultivating the powers of observation in childhood. It is claimed that this is a beginning in science; and, as it brings the mind into action upon things, is a corrective of the inordinate study of words. But object teaching has not yielded what was expected of it; and is in no true sense a first step in science. Nothing is gained educationally by barely having an object in hand when it is talked about. Myriads of objects are present to the senses of peoAs thus treated the sciences have but ple but no insight follows. The observvalue in education. They fall below ing faculties must be tasked if they are other studies as means of mental culti- to be trained. The pupil is not to have vation. Arithmetic arouses mental re- the properties of objects pointed out, action. The rational study of language, but he is to find them out. Science will by analytical and constructive tasks and do its work of educating the observing the mastery of principles, strengthens faculties only as they are quickened and the mental processes; but the sciences sharpened by exercise in discrimination. are not employed to train the faculties The scientific aim is to replace vague conin the various ways to which they are fused impressions by clear and accurate severally adapted. They are not made ideas. Skill in the detection of nice disthe means of cultivating the observing tinctions is only gained by prolonged powers, stimulating inquiry, exercising and careful practice. Object lessons afthe judgment in weighing evidence, nor of forming original and independent habits of thought. The pupil does not know the subjects he professes to study by actual acquaintance with the facts, and he therefore becomes a mere passive accumulator of second-hand statements. But it is the first requirement of the scientific method, alike in education and in research, that the mind shall exercise its activity directly upon the subject matter of study. Otherwise scientific knowledge is an illusion and a cheat. As science is commonly pursued in book descriptions the learners cannot even identify the things they read about. As remarked by Agassiz, "the pupil studies Nature in the school-room, and when he goes out of doors he cannot find her." This mode of teaching science, which is by no means confined to the public schools, has been condemned in the most unsparing manner by all eminent scientific men as a deception," a "fraud," an outrage upon the minds of the young, ," and " an imposture in education." Nor has this criticism of bad practices been without its effect. We are met by the statement that much has been done in the public schools to escape the evils of mere book science. The method of object lessons has been extensively introduced into primary schools with the pro

ford no such cultivation. We do not say they are useless, but they are not the A B C of science, and do not, as a matter of fact, open the way to the proper study of the special sciences. This is their test and their condemnation. When the primary pupils have gone over their prescribed course of object lessons, and are passed on to a higher grade, strange to say the "objects" are suddenly dropped as if the objective method had been exhausted. In the technical phrase perceptive education is to be replaced by conceptive education. Instruction in elementary science is now to be carried on by what is known as oral teaching. This method as extensively practised in the grammar grades of the public schools is every where growing in favor, and we are once more told that it is a successful revolt against book studies. It is chiefly applicable to the sciences and its cardinal idea is instruction without a text book. This looks fair but it is delusive. The method does not remove the book that the pupil may come at the phenomena, but it removes the book that the teacher may take its place. Oral teaching is class instruction, in which information is imparted in a familiar manner with the view of awakening the interest of the class. But so far as real science is concerned it is doubtful if this method