« السابقةمتابعة »
as the light emerged from the substance, the plane of polarisation was observed, by noting the position of the analyser when it cuts off the ray. A powerful magnetic force was then made to act, so that the lines of force within the substance coincided with the direction of the ray. Under these conditions Faraday discovered that the effect of the magnetic field was to turn the plane of polarisation through a small angle, round the direction of the ray as an axis ; the direction of rotation was the same as that of the positive current in the electro-magnet. Besides heavy glass, numerous other transparent bodies have been tried with a similar, though less effect; in the case of certain salts of iron the rotation is, however, the reverse of that just stated.
The physical explanation of Faraday's discovery is doubtless to be found in the molecular change impressed on the transparent body submitted to the magnetic force. A plane polarised ray may be
. regarded as consisting of two circularly polarised rays moving in opposite directions, and of these two rays that moving in the righthanded direction has, by the act of magnetisation, performed a greater number of vibrations in the same period than the left
In other words, the index of refraction of the glass for one of these circularly polarised rays has been altered by the molecular stress produced by the magnetic force. For if the heavy glass be suspended between the poles of the magnet, it is repelled, as Faraday subsequently discovered, from both poles, so that it sets across the lines of force that stream from pole to pole : what is true of the glass as a whole must be equally true of the molecules of the glass, hence the production of the molecular stress to which we have referred.
Many of our readers are probably aware of the fact that there are certain substances which, independently of magnetic force, rotate the plane of polarisation as the ray passes through the substance. There is this radical difference, however, between such natural rotation, and that induced by magnetic action, viz. in the former case the direction of rotation is reversed when the direction of the ray is reversed, and in the latter case the direction of rotation is exactly the same, whichever way the ray passes along the substance, the direction of rotation only being reversed by reversing the magnetic poles. Hence it is possible, by reflecting a ray to and
fro along a diamagnetic body, to increase the amount of rotation considerably.
M. H. Becquerel has recently shown that the phenomena of magnetic rotation are not only a function of the wave length of the light used, but also of the index of refraction, and of the chemical composition of the bodies employed.
A new and surprising discovery in connection with this subject was published by the Rev. Dr. Ker, at the last meeting of the British Association. Dr. Ker's discovery consists in this, that he has acted upon a polarised light by magnetism, without the intervention of any solid or liquid medium. By simply reflecting a ray of plane polarised light from a polished surface of iron, Dr. Ker has obtained an effect analogous to Faraday's discovery, whenever the iron mirror is intensely magnetised. By proper precaution, Dr. Ker has prevented the reflected ray from being elliptically polarised by the act of metallic reflection; and he finds that at oblique incidence, when the iron is made a south pole the ray is turned to the right, when a north pole to the left; the current which magnetises the iron carrying, as it were, the plane of polarisation with it.
This Faraday's effect over again, only with reflection from a surface, instead of transmission through a body. Hence it is probable the effect is due to a molecular change, impressed on the iron by the act of magnetisation. If this be so, gilding or silvering the magnetic pole should prevent the occurrence of the phenomenon, though it would not prevent the free action of magnetic force upon the polarised ray, if simply due to this cause. This crucial experiment has just been tried by Mr. Fitzgerald, of Trinity College, Dublin, with precisely the results anticipated by the writer. Mr. Fitzgerald has also given, but not yet published, an explanation of Dr. Ker's phenomenon, based upon a change in the index of refraction of the iron by the act of magnetisation. Experiments will shortly be in progress for the examination of the effect of perpendicular incidence upon the magnetic pole—a point of much theoretic importance. Meanwhile we await with much eagerness Dr. Ker's fuller publication of his discovery, and his further researches therein, and in conclusion join our congratulations to those which Dr. Ker has already received for the invaluable contributions to natural knowledge which he has already given to the world.
How to Succeed in Life : a Guide to the Young. By the Rev. J. B.
LISTER. 4th Edition. London: J. Snow & Co. Much excellent advice is given here in a small compass, touching life at school and at home, business and religion. Moreover, it is given in a way that will render it palatable even to those who have arrived at an age when the desire to think and act for themselves is specially strong
The Spiritual World, and our Children there. By the Rev. CHAUNCEY
GILES. London: J. Spiers. WITHOUT question, there is something very attractive in the teaching of Swedenborg as to the spirit world; and the author of this treatise, who is a believer in the New Church doctrines, writes with all the zeal of an enthusiast. Whether agreeing with his views or not, we cannot help feeling an interest in watching the skilful manner in which they are developed. Wherein his beliefs go beyond those of other Christians, they rest upon a priori arguments, and the revela
à tions which the founder of the sect professed to have received. In respect of the former, there is a good deal which we cannot help regarding as not proven; while the latter furnish us with minutiæ of detail about the other world and the state of the soul after death, which we think would have been revealed eighteen centuries ago had it been intended that we should know them. The first chapter is the most difficult of all to accept, and this is indeed essential to the whole argument; but notwithstanding we find an obstacle here, we fully endorse many of the author's criticisms of popular beliefs, and his strenuous contention that the true life of man will be hereafter. Mors janua vita is one of the cardinal doctrines of this school of theologians, and they enforce it with a vigour well worthy of imitation.
The High Places of the Bible. By the Rev. JOHN THOMAS. London :
F. E. Longley A SERIES of thirteen sermons on the great scenes for which some of the heights in Sinai, Moab, and Palestine are specially memorable. The descriptions are graphic, and the lessons drawn are appropriate,
Lectures to Professing Christians. By the Rev. Professor Finney.
London: F. E. Longley. PROFESSOR Finney was a man of strong opinions and of plain language. He expressed what he felt with all the force and directness of utterance of which he was master. He had no notion of concealing his message in smooth-sounding phrases for fear of offending his auditory. These lectures will be found well worthy of study, , though they have some of the imperfections inseparable from condensation at the hands of the reporter. On our library table we have also a number of smaller publications. -Biographical Notes on John Foxe, the Martyrologist, by WILLIAM WINTERS, F.R.Hist.Soc. A brief sketch of his life and that of his more immediate descendants, chiefly collected from original MSS., some in the possession of the author. From the parish registers of Waltham Holy Cross, we find the family name spelt in five different ways within 150 years-Foxe, Foex, Ffoxe, Fox, and Ffox. As a specimen of how to keep a parish register we quote an entry under the year' 1706,—“A nursechild from foxes-buried Dec. 20.” Some of the entries in the Cheshunt register are scarcely more definite, as e.g., " 1566. The wife of fox, buried Nov. 16."--The Laws of God v. the Laws of Men, or the Year of Jubilee and the Millennium,* is a pamphlet advocating the universal application of the land laws laid down in the Books of Moses for the Children of Israel. Large landowners in this country will regard it as revolutionary.-One of real interest is the reprint of “A Narrative of the Proceedings of a Great Council of Jews, assembled in the Plain of Ageda, in Hungaria, about 30 leagues distant from Buda, to examine the Scriptures concerning Christ, on the 12th of October, 1650, by SAMUEL BRETT, there present. At this Council, it appears, no Jews were admitted but those who could prove their descent in the most orthodox manner, and then, the formalities being over, the Scriptures were examined concerning Christ. On the seventh day of their deliberations they called in six clergy sent from Rome to hear what they had to say on the subject, but the Jews were so scandalised at their doctrines that they cried out, “No Christ, no woman god, no intercession of saints, no worshipping of images,” &c., and the Council broke up, not to be
* S. Harris & Co.
+ Longmans & Co.
renewed again.—Thorough English, by A. J. D. D’ORSEY, B.D.,* is the reprint of an article containing, “ Hints to Teachers with regard to Composition,” well deserving of consideration. It has often struck us as most lamentable that youths educated at our public schools should, on entering upon the business of life, be generally unable to write correctly in their mother tongue. Mr. D'Orsey's hints are certainly much needed.—In the North of England Tractates, No. 12,is an account of “ The Saxon Cross, Church, &c. of Dewsbury," by J. R. Robinson, LL.D., &c. This church is of no little interest to the antiquarian, and its foundation can be traced back to Paulinus, the Roman missionary and first Archbishop of York. The narrative is accompanied by drawings of the most curious remains.Outside the Fold, by T. W. AVELING, D.D., I is the address delivered at the recent meeting of the Congregational Union on the external relationships of Congregational Churches.” It is full of good thoughts, and will well repay perusal. Would that the correspondents of religious papers would take the hint given them on page 36, as to “the most trivial facts—interesting, no doubt, to the parties themselves," being “trumpeted to the whole world, that cares nothing about them.”—Perfect, but not Perfected, § is the title of an address by the Rev. C. O. ELDRIDGE, B.A., on entire sanctification in its relation to growth in grace.—The Oriental Star is a new weekly, edited by Mr. J. LEWIS FARLEY, advocating the cause of the Christians in the East of Europe. The Editor's personal knowledge of the state of affairs in Turkey will serve to guarantee the trustworthiness of its contents. The Journal of Education || for the last three months has contained reprints of some valuable papers on Education, read at the meeting of the British Association, the Social Science Congress, and other gatherings of similar character.-The Medium and Daybreak, 1 is a weekly journal devoted to the subject of spiritualism, but as Dr. Slade and other leading spiritualists are now in the hands of the law courts we will not venture any opinion as to the contents of the paper, and only express our astonishment at the number of works on the subject which appear in its advertising columns.
* Simpkin, Marshall & Co.
Hodder & Stoughton.
+ Tweddell & Sons, Stokesley.