UNIVERSITY AND EDUCATIONAL INTELLIGENCE.

OXFORD.-The first election to a Geographical Studentship will be held at the end of Hilary Term 1892. The student at the time of his election must have passed all the examinations for his B. A. degree in the University of Oxford, but must not be of more than eight years' standing from matriculation. Pre

vious to his election he must have atten led the lectures of the Reader in Geography in at least two terms. Information as to the conditions of tenure may be obtained from the Reader in Geography.

The Report of the Delegacy of Non-Collegiate Students was presented to Convocation on Wednesday. It shows that the list of matriculations is rather larger than in the preceding year, but the total number of undergraduates has somewhat decreased. The total number on the books (440) is the largest which has yet been reached. Thirty-six took the B. A. degree, and nineteen the M. A. during the year. The Delegates notify that they admit, without examination, students in any special branch of study who do not desire to pass through the Arts course, and can show evidence of fitness for their special subject. Sixteen students have availed themselves of this privilege during the year. The balance-sheet appended shows that the financial condition is satisfactory. The total receipts exceeded the expenditure by £550, and the accumulated balance in the hands of the Delegacy at the close of the year was £2284.

CAMBRIDGE.-Mr. J. Macalister Dodds, of Peterhouse, has been elected Chairman of the Examiners for the Mathematical Tripos, Part I.

A petition from 2689 pe sons residing in New Zealan has been received by the Vice-Chancellor, praying that the Senate will grant degrees to properly qualified women. The signatories include Sir George Grey, K.C.B., formerly Governor of New Zealand, most of the Ministers of the Colonial Government, and many professors and graduates of the University of New Zealand.

Lord Wal-ingham, F.R.S., High Steward of the University, offers annually a gold medal to B.A.'s of not more than two years' standing for the best monograph or essay giving evidence of original research on any botanical, geological, or zoological subject; zoology being understood to include animal morphology and physiology, and an essay on any subject of chemical physiology being valued according to its physiological rather than its chemical importance.

MR. K. W. STEWART, B.Sc. (Lond.), has been appointed Assistant Lecturer and Demonstrator in Physics at the University College of North Wales, Bangor.

SCIENTIFIC SERIALS.

THE American Meteorological Journal for October contains:-A short memoir of the late Prof. W. Ferrel, by Prof. A McAdie, with a complete list of his scientific contributions, from 1853 to 1891; his last paper, which appeared in our columns in April 1891, was entitled "The High-pressure Area of November 1889 in Central Europe."-The mineral waters of Vosilanti and other places in Michigan, by Dr. E. N. Brainerd.Cloud observations at sea, by Prof. C. Abbe. This is a preliminary report relative to the principal features of the work done by him during the recent cruise of the Pensacola to the West Coast of Africa. A number of experiments were made to determine the relative speed and direction of movement of the various strata of air, by means of clouds and small balloons. The experiments showed that the use of balloons is practicable both on sea and land, and gives accurate results. The following are some of the results of the author's observations: the vertical circulation increases and the horizontal circulation diminishes in the doldrums; the horizontal movement is a maximum at high latitudes; the bases of the cumuli are lower and their tops higher in the low latitudes; if there be any general east wind in the upper regions at the doldrum it is above the clouds, and therefore not observable. The last article is by

Dr. Leudet, on the action of climates at elevated stations on diseases of the chest.

Bulletin de l'Académie des Sciences de St. Pétersbourg, new series, vol. ii., No. 1.-On the scales of Holoptychius found in Russia, by Dr. Rohon (French). The histology of the same is

described, as also two new species: Hol. virius and Hol. superbus.-Ichthyological notes from the Museum of the Academy, by S. Herzenstein, being a description of the following new species: Cottus nivsus, Centridermichthys alcicornis, Hypsagonus gradiens, Stichæus grigoriewi, St. dicty grammus, Chirolophus japonicus, Pleuronectes obscurus, Pl. japonicus, Pl. bicoloratus (incompletely described by Basilewsky), Hippoglossus grigoriewi, Alburnus charusini, and Nemachilus kuschake witschi.-On the extraordinary pheno nena presented by the great comet of 1882, by Th. Bredichin. After having given in a preceding paper his reasons for considering the interior tube of that comet as an anomalous tail, the author applies the same explanation to the exterior tube. -On two new laws of celestial mechanics, by H. Struve. In addition to the previously communicated results of observations made on the satellites of Saturn with the 30-inch refractor, Prof. Struve points out the remarkable relations which exist between the satellites Mimas and Tethys on the one side, and Enceladus and Dione on the other side. The observations of Mimas bave shown that its orbit has an inclination of 1° 26' on the equator of Saturn, and that its nodes have a motion of 1° every day, so that by the end of the year the orbit returns to its previous position; moreover, a considerable acceleration has been noticed in the rotation of Mimas during the last few years. From these facts M. Struve deduces the following law:-"Four times the average movement of Tethys, minus twice the average movement of Mimas, is always equal to the sums of the average movements of the nodes of the orbits of Mimas and Tethys on the equator of the planet." The same law may also be expressed in this way:-"(1) The conjunctions of Mimas and Tethys always take place about a point which is situated halfway between the ascending nodes of their orbits on the equator of Saturn. They may move off this point for about 48°, and this libration is performed in sixty-eight years. (2) The conjunctions of Enceladus and Dione always coincide with the perisaturn of Enceladus, or, at least, they must oscillate around this point." Several important conclusions relative to the mass of Rhea and that of the rings may be deduced from these laws. -On the genus Obolus (Eichwald), by A. Mickwitz.-On a personal equation in photometric observations of stars, by E. Lindemann.-The mammals of the Gan-su expedition of 188487, by Eug. Büchner (German). The few species of this very interesting fauna which have been brought to St. Petersburg, are described, the remainder being kept in the Museum of Irkutsk. On the rotation of Jupiter, by A. Belopolsky (in the rotation-period to be equal to 9h. 55m. in the latitudes German). From a perusal of all available data, the author finds from 10 to 45°, while in the zone o° to 5°, it is only 9h. 50m.On the Ammonites of the Artinsk strata, by A. Karpinsky (German). The collection is derived from North-East Russia; the new species are: Pronorites postcarbonicus, Pr. præfermicus, Paratronorites tenuis, Gastrioceras suessi, Agathiceras uralicum, Popanoceras krasnopolskyi, and Thalassoceras gemmellaroi. —On a new process for separating iron-oxide from aluminium, by F. Beilstein and R. Luther.-Chemical notes, by N. Beketoff.On the use of incandescent light for self-registering instruments, by H. Wild.-On artificial amphibolite, by K. Khrustschoff.

IN the Botanical Gazette for September and October, Mr. T. Holm continues his series of articles on the minute comparative anatomy of American grasses. Brief abstracts are given of the botanical papers read at the Washington meeting of the American Association for the Advancement of Science, and at that of the Botanical Club of the same Association. Other papers are chiefly of interest to American botanists.

SOCIETIES AND ACADEMIES.
LONDON.

Zoological Society, November 3.-Prof. W. H. Flower, F.R.S., President, in the chair.-The Secretary read a report on the additions that had been made to the Society's Menagerie

during the months of June, July, August, and September, 1891, and called attention to certain interesting accessions which had been received during that period.-The following objects were exhibited :-(1) On behalf of Mr. F. E. Blaauw, a stuffed specimen of a young Wondrous Grass-Finch (Poephila mirabilis), bred in captivity at his house in Holland; (2) on behalf of Prof. E. C. Stirling, a water-colour drawing of the new

Australian Mammal Notoryctes typhlops; (3) by Mr. G. A. Boulenger, an Iguana with the tail reproduced; (4) by Mr. R. Gordon Wickham, a very fine pair of horns of the Gemsbok (Oryx gazella) from Port Elizabeth, South Africa; and (5) by Dr. Edward Hamilton, a photograph of an example of the Siberian Crane (Grus leucogeranus), shot on the i-land of Barra, Outer Hebrides, in August last.—Mr. R. Lydekker give a description of some Pleistocene Bird-remains from the Sardinian and Corsican Islands. These belonged mostly to recent forms, but to genera and species which in several instances had not been found fossil. They showed rather more of an African character than the present avifauna of these islands.—Mr. R. Lydekker also read some notes on the remains of a large Stork from the Allier Miocene. These remains were referred to the genus, closely allied to Ciconia, lately named Pelargopsis, but which (that term being preoccupied) it was now proposed to rename Pelargoides.-Mr. R. Lydekker also exhibited and made remarks on the leg-bones of an extinct Dinornithine Bird from New Zealand, upon which he proposed to base a new species allied to Pachyornis elephantopus (Owen), and to call it, after the owner of the specimens, Pachyornis rothschildi.-Dr. A. Gunther, F. R.S., read a description of a remarkable new Fish from Mauritius belonging to the genus Scorpana, which he proposed to call Scorpæna frondosa.-A communication was read from Mr. Roland Trimen, containing an account of the occurrence of a specimen of the scarce Fish Lophotes cepedianus, Giorna, at the Cape of Good Hope.-A communication was read from the Hon. L. W. Rothschild, giving a description of a little-known species of Papilio from the Island of Lifu, Loyalty Group. Mr. R. J. Lechmere Guppy read some remarks on a fine specimen of Pleurotomaria from the island of Tobago.-A communication was read from Mr. L Péringuey, giving an account of a series of Beetles collected in Tropical Southwestern Africa by Mr. A. W. Eriksson.

Mr.

Entomological Society, November 4.-Dr. D. Sharp, F.R.S., Vice-President, in the chair.-Mr. W. F. Kirby exhibited a series of a very dark-coloured form of Apis reared by Mr. John Hewitt, of Sheffield, from bees imported from Tunis, and which he proposed to call "Punic bees."-Mr. C. G. Barrett exhibited five melanic specimens of Aplecta nebulosa, reared from larvæ collected in Delamere Forest, Cheshire, and described in the Proceedings of the Lancashire and Cheshire Natural History Society as A. nebulosa, var. Robsoni. Barrett also exhibited a beantiful variety of Argynnis aglaia, taken in Norfolk by Dr. F. D. Wheeler, and two specimens of Lycana argiades, taken in August 1885, on Bloxworth Heath, Dorsetshire. -Mr. H. St. John Donisthorpe exhibited a collection of Coleoptera, comprising about thirty-six species, made in a London granary in 1890 and 1891. The genera represented included Sphodrus, Calathus, Quedius, Creophilus, Omalium, Trogosita, Silvanus, Lathridius, Dermestes, Anthrenus, Ptinus, Niptus, Anobium, Blaps, Tenebrio, Calandra, and Bruchus.Mr. A. B. Farn exhibited a series of specimens of Eubolia lineolata, bred from a specimen taken at Yarmouth. The series included several remarkable and beautiful varieties, and the size of the specimens was much above the average.-The Rev. Dr. Walker exhibited specimens of Argynnis ino and A. pales, from Norway. Mr. B. A. Bower exhibited, for Mr. J. Gardner, specimens of Nephopteryx splendidella, H. S., Botys lupulinalis, Clk., and Bryotropha obscurella, Hein., taken at Hartlepool.Mr. R. Adkin exhibited two very dark specimens of Peronea cristana, from the New Forest.-Colonel C. Swinhoe exhibited, and remarked on, types of genera and species of moths belonging to the Tineina, all of which had been described by Walker, and placed by him amongst the Lithoside.-Mr. H. Goss exhibited specimens of Callimorpha hera, taken by Major General Carden in South Devon in August last, and observed that the species appeared to be getting commoner in this country, as General Carden had caught seventeen specimens in five days. Mr. Goss said that the object of the exhibition was to ascertain the opinion of the meeting as to the manner in which this species had been introduced into this country. A discussion on the geographical distribution of the species ensued, in which Mr. G. T. Baker, Colonel Swinhoe, Mr. McLachlan, Mr. Verrall, Captain Elwes, Mr. Barrett, Mr. Fenn, and others took part. -Mr. C. J. Gahan contributed a paper entitled "On South American Species of Diabrotica," Part III.-Mr. McLachlan contributed a paper entitled " Descriptions of New Species of Holopthalmous Ascalaphide."-Mr. W. L. Distant communi. cated a paper entitled "Descriptions of Four New Species of

the Genus Fulgora."-Mr. F. Enock read a paper entitled "Additional Notes and Observations on the Life-history of Atypus piceus.' Every detail in the life-history of this spider was most elaborately illustrated by a large number of photographs, made by Mr. Enock from his original drawings, and shown by means of the oxy-hydrogen lantern. A discussion followed, in which Mr. C. O. Waterhouse, Dr. Sharp, Mr. G. C. Champion, the Rev A. E. Eaton, and Mr. P. Crowley took part.

Anthropological Institute, November 10.-Dr. Edward B. Tylor, F.R.S., President, in the chair.-Mr. Francis Galton exhibited, on behalf of Lady Brooke, a photograph of a human figure carved on a rounded sandstone rock in Sarawak ; the rock is about twelve feet in height, and the sculpture is in high relief and of the size of life. Mr. Galton also exhibited some imprints of the hand, by Dr. Forgeot, of the Laboratoire Criminale, Lyon.-Dr. Tylor read a paper on the limits of savage religion. In defining the religious systems of the lower races, so as to place them correctly in the history of culture, careful examination is necessary to separate the genuine developments of native theology from the effects of intercourse with civilized foreigners. Especially through missionary influence since 1500, ideas of dualistic and monotheistic deities, and of moral government of the world, have been implanted on native polytheism in various parts of the globe. For instance, as has lately become clear by the inquiries of anthropologists, the world-famous Great Spirit of the North American Indians arose from the teachings of the Jesuit missionaries in Canada This and analogous names early in the seventeenth century. for a Supreme Deity, unknown previously to native belief, have since spread over North America, amalgamating with native doctrines and ceremonial rites into highly interesting but perplexing combinations. The mistaken attribution to barbaric races of theological beliefs really belonging to the cultured world, as well as the development among these races of new religious formations under cultured influence, are due to several causes, which it is the object of this paper to examine: (1) direct adoption from foreign teachers; (2) the exaggeration of genuine native deities of a lower order into a God or Devil; (3) the conversion of native words, denoting a whole class of minor spiritual beings, such as ghosts or demons, into individual names, alleged to be those of a Supreme Good Deity or a rival Evil Deity. Detailed criticism of the names and descriptions of such beings in accounts of the religions of native tribes of America and Australasia was adduced, giving in many cases direct proof of the beliefs in question being borrowed or developed under foreign influence, and thus strengthening the writer's view that they, and ideas related to them, form no original part of the religion of the lower races. The problems involved are, however, of great difficulty, the only hope of their full solution in many cases lying in the researches of anthropologists and philologists minutely acquainted with the culture and languages of the districts; while such researches will require to be carried out without delay, before important evidence, still available, has disappeared.

PARIS.

Academy of Sciences, November 9.-M. Duchartre in the chair. On the use of chronophotography for the study of machines constructed for aërial locomotion, by M. Marey. It is known that, in the case of a plane moving in a fluid medium, the centre of pressure only coincides with the centre of figure if the plane be normal to the direction of its motion; but if the plane makes an angle with its trajectory, the centre of pressure occurs in advance of the centre of figure to an extent which increases as the plane forms a more acute angle with the direction of motion, and as its velocity of translation is increased. This principle is strikingly illustrated by some photographs of a specially constructed falling body taken at intervals of a twentieth of a second. The body first described a sensibly parabolic curve, it then rose slightly, and passed over a convex curve before reaching the ground. The figure accompanying the paper shows clearly that the inflexions of the body's trajectory depend on the variations of its velocity, and the inclination of its surface with respect to the direction of motion.-On the laws of the intensity of light emitted by phosphorescent bodies, by M. Henri Becquerel. The author develops formulæ to represent the relation between the intensities of light emitted by phosphorescent bodies and the duration of illumination, and compares the results of some of

his father's observations with those obtained by calculation. The agreement of the two sets of numbers is very close, even when the intensity was taken some thirty minutes after the body had been emitting light. A relation is also established between the intensity and the time that the body was exposed to light. Study of boron phospho-iodides, by M. Henri Moissan. (See Notes, p. 67.)-M. Haton de la Goupillière made some remarks on the paper read by Sir William Thomson before the Royal Society on April 9, "On Electrostatic Screening by Gratings, &c.," saying that he had published some similar results in 1859. Experimental determination of the velocity of propagation of electro-magnetic waves, by M. R. Blondlot. Experiments have been made between wave-lengths 8.94 and 35 36 metres, and the results show that all electrical undulations have a velocity of propagation of about 297,600 kilometres per second. On algebraic integrals of the differential equation of the first order, by M. Autonne.-On surfaces with rational generators, by M. Lelieuvre.-Theory of turbo-machines, by M. Rateau.-A simple method of verifying the centres of the object-glasses of microscopes, by M. C. J. A. Leroy.—On the existence of acid or basic salts of monobasic acids in very dilute solutions, by M. Daniel Berthelot. The author has studied very dilute solutions near the point of neutralization, using HCl and baryta water at a concentration of oor equivalent per litre, by the method of measuring the electric conductivities. He concludes that acid and basic salts are not destroyed by dilution, even very dilute solutions containing traces undecomposed.-On the formation of hydrates at high temperatures, by M. G. Rousseau.-On a double chloride of copper and lithium, by M. A. Chassevant. A substance of the composition 2 CuCl. LiCl} + 5H2O has been obtained. It is decomposed by water, but is soluble to a red-brown solution in a concentrated solution of lithium chloride from which it may be recrystallized. -Researches on digitalein, by M. J. Houdas. -On isocinchonines, by MM. E. Jungfleisch and E. Leger.-Estimation of fats in milk products, by MM. Lezé and Allard. - Ptomaïnes extracted from urine in cases of some infectious maladies, by M. A. B. Griffiths. The ptomaine from scarlet fever has the composition CH12NO, that from diphtheria C1H17N2O ̧ ; they have also been prepared from pure cultures on peptonized gelatine of Micrococcus scarlatina and Bacillus diphtheria respectively. The ptomaïne from the urine of a case of mumps has the constitution NH: C(NH). N(C3H7). CH2.CO2H. None of the three ptomaïnes described are constituents of normal urine.-On the exterior form of the muscles of man with respect to the movements executed (experiments made by chronophotography), by M. G. Demeny.-On the formation of the peripheral nervous system of vertebrates, by M. P. Mitrophanow.-On the effects of parasitism on Ustilago antherarum, by M. Paul Vuillemin.Meteorological observations made at Rodez, by M. des Vallières.

AMSTERDAM.

I

17

Royal Academy of Sciences, October 31.-Prof. van de Sande Bakhuyzen in the chair.-Prof. P. H. Schoute offered some general remarks on Lemoine's two problems of stamps: In how many different ways a ribbon of stamps and a rectangular sheet of pq stamps can be folded up in one? (compare vol. i. p. 120 of the "Théorie des Nombres "of E. Lucas). He reduced the first problem to a question in the theory of permutations, gave the number x of its solutions up to pq, and showed why the number xpig of the solutions of the second problem must surpass the expression (+22) xp xq. — Prof. B. J. Stokvis Prof. B. J. Stokvis made a contribution to our knowledge of mutual antagonism and the combined action of mutual antagonists. In experimenting on the isolated and freely pulsating frog's heart, he stated that digitaline on the one side, and muscarine (or chinine) on the other, were to be considered as mutual antagonists for this organ, and displayed their antagonistic action, whichever of the two might be applied first. In another series of experiments he studied the action of muscarine and digitaline flowing at the same time with the nourishing blood through the isolated frog's heart, and found that the greatest antagonistic action, for instance of digitaline, was displayed when very dilute solutions (1 25,000 or I: 33,333) were applied at the same time as moderately strong solutions of muscarine. Finally, he stated that the isolated frog's heart recovered much faster and much more easily by normal blood when it was previously poisoned by muscarine and digitaline combined than when it was poisoned

BOOKS, PAMPHLETS, and SERIALS RECEIVED. BOOKS.-The Land of the Lamas, W. W. Rockhill (Longmans).-Arphimixis; oder Die Vermischung der Individuen : A. Weismann (Jena, Fischer).-Primitive Culture; 2 vols., 3rd edition, revised: Dr. E. B. Tylor (Murray).-Memoirs of the Geological Survey of India, vol. xxiii. Geology of the Central Himálayas: J. L. Griesbach (Calcutta).-L'Homme dans la Nature: P. Topinard (Paris, Alcan).-Outlines of Physiological Chemistry. 2nd edition: F. C. Larkin and R. Leigh (Lewis).-My Personal Experiences in Equatorial Africa: T. H. Parke (Low).-An Introduction to the Theory of Value: W. Smart (Macmillan).-Quantitative Chemical Analysis: F. Clowes and J. B. Coleman (Churchill).-A Hand-book of Industrial Organic Chemistry S. P. Sadler (Lippincott).-Farm Crops; J. Wrightson (Cassell). -Our Common Birds and how to Know Them: J. B. Grant (Gay and Bird). -The Microscope and its Relations, 7th edition: Dr. W. H. Dallinger (Churchill).-How to Use the Aneroid Barometer: E. Whymper (Murray). -Beobachtungen der Russischen Polar-station auf Nowaja Semlja, 1 Theil, Magnetische Beobachtungen: K. Andrejeff (St. Petersburg). Selected Essays of Arthur Schopenhauer: E. B. Bax (Bell).-About Ceylon and Borneo: W. J. Clutterbuck (Longmans).-With Axe and Rope in the New logy, Part 1, The Microscope and Microscopical Methods: S. H. Page Zealand Alps: G. E. Mannering (Longmans).-The Microscope and Histo(Ithaca, N. Y.).-Anthropogenie oder Entwickelungsgeschichte des Menschen, 2 vols. E. Haeckel (Leipzig, Engelmann).

PAMPHLET.-A Memoir on the Coefficients of Numbers: B. Seal (Calcutta).

SERIALS.-Bacteriological World, vol. i. No. 10 (Battle Creek, Mich.).— Proceedings of the Aristotelian Society, vol. i., No. 4, Part 2 (Williams and Norgate).-Himmel und Erde, November (Berlin, Paetel).-Bulletin de l'Académie Impériale des Sciences de St. Pétersbourg, nouvelle série ii. (xxxiv.) (St. Pétersbourg).-Harvard University Bulletin, No. 50.

THURSDAY, NOVEMBER 26, 1891.

ELECTRO-MAGNETISM.

The Electro-magnet and Electro-magnetic Mechanism. By S. P. Thompson, D.Sc., F.R.S. (London: E. and F. N. Spon, 1891.)

THIS

HIS is a reprint, with additions, of a course of Cantor Lectures which the author delivered during 1890 before the Society of Arts. The book, it may be stated at the outset, is an excellent account of electro-magnetic mechanism, and abounds in information at once of historical, scientific, and practical value. Evidently the author is willing to spare no pains to give completeness to any work of this kind he undertakes, and the present book, like his treatise on dynamo-electric machinery, will no doubt be widely read and appreciated.

In the preface, and elsewhere in the body of the book itself, Dr. Thompson indulges in some statements which we think are a blemish on an excellent and well-written treatise. It serves no good purpose to distribute in a scientific book praise or blame to certain classes of scientific investigators, and while glorifying a certain section of workers, to pour what seems little short of contempt and derision on the labours of another. We refer here to the statements (chiefly in the preface) regarding the earlier mathematical theories of magnetism, and their alleged influence in retarding electro-magnetic discovery.

It is quite true that some of the older theorists, concentrating their attention on the magnetic field of a system of permanent magnets, gave only a secondary attention to the problem of the internal constitution of a magnet. But it is hardly fair to put down against them, by inference, the errors of the persons who persisted in assuming that, because it had been proved that a magnet produces a field which can also be accounted for by a distribution of imaginary magnetic matter over the surface of the magnet, the magnetization of the magnet did consist in such a distribution. Such an equivalent distribution is a conception helpful in itself, inasmuch as it can be experimentally determined, and expresses exactly the manner in which the lines (unit tubes) of magnetic induction leave the surface. But to accuse it of misleading those who misunderstood it, is to put on the shoulders of Gauss and others who considered surface distributions a responsibility which is not theirs, and a blame which properly belongs to the perverse experimentalists who have insisted on determining the actual positions of "poles" in bar magnets, and on measuring other things equally indeterminate or non-existent.

But is the following statement quite free from possibility of misconstruction? " Gradually, however, new light dawned. It became customary, in spite of the mathematicians, to regard the magnetism of a magnet as something that traverses or circulates around a definite path, flowing more freely through such substances as iron than through other relatively non-magnetic materials." If any student of the subject does get into his head the idea that an actual material something flows round a magnetic circuit, he might quite as justly hold Dr. Thompson responsible for this false notion as blame the mathe

maticians for causing him to suppose a magnet to be a body plastered over with imaginary magnetic matter.

66

In tracing the evolution of the notion of magnetic permeability, Dr. Thompson might have made some mention of the contributions to molecular theory given by Poisson and others; for after all, these men really knew as well as we do "that magnetism, so far from residing in the end or surface of the magnet, is a property resident throughout the mass." But, as has already been stated, their attention was chiefly directed to the fields of permanent magnets; and to find a doctrine which "will afford a basis of calculation such as is required by the electrical engineer" is the business of the electrical engineer himself, and others interested in the problem Hitherto, indeed, so far as such a doctrine has been found, it has been discovered in great measure by the physical mathematician! The mathematical doctrine o magnetic permeability," or-to use Faraday's phraseconductivity for magnetic lines of force," was given so long ago as 1872 by Sir William Thomson, and fully illustrated by analogies and applications; and it is certainly curious that so accurate an historian as Dr. Thompson should, in his historical résumé, have made no mention of this very important paper. It is also the fact that our knowledge of the properties of iron, which, with the "simple law of the magnetic circuit," constitutes, according to Dr. Thompson, the stock-in-trade of the designers of dynamos, has come in no small degree from the same source. The most eminent investigator and improver of the dynamo is also a mathematician; but perhaps, as Sir William Hamilton (of Edinburgh, not of Dublin) said of a certain mathematician who, he was forced to admit, reasoned correctly, he did it in spite of his mathematics, not because of them.

All honour to the great mathematicians who first attacked the difficult subject of magnetic action. But even if they had sinned so grievously by their unpracticality as it seems now the fashion to try to make out, their successors, entering into their labours, have been able to do much to atone by helping the engineer in the difficulties which beset his advance into a region, viewed indeed from afar, but hitherto untrodden. In this great work the engineer and mathematician are necessarily companions, and for either to reproach the other, as to what happened or did not happen in the past, is only to provoke useless recrimination, and delay their onward progress.

It is time now to come to the subject-matter proper of the book, and for this we have, on the whole, nothing but commendation. There are some things which might, perhaps, have been expressed differently with advantage, but this, of course, is only a matter of opinion. In the first chapter a very interesting account is given of the inventions and researches carried out by Sturgeon, Henry, and Joule, and ends with a description of notable electro-magnets. The sketch of Sturgeon's career, given in an appendix to this chapter, is of remarkable interest as a plain unvarnished record of heroic toil in the pursuit of knowledge, carried on amid uncongenial surroundings, and in spite of the hard pinch of poverty. In happier circumstances, this experimental genius would no doubt have done much for science. Still, to us there is some compensation, for, had it not

been for the res angusta domi of his later years, we might not have had his "Annals of Electricity" or his " Scientific Researches." As it is, it seems well established that he was the pioneer of electro-magnetic discovery, the maker of the first electro-magnet and the first magneto-electric machine; and Dr. Thompson has done a simple act of justice in bringing Sturgeon's claims in this respect before the great public now interested in the progress of electrical science.

In chapter ii. we have generalities concerning electromagnets and electro-magnetism, descriptions of typical forms of electro-magnets, and materials of construction. First are discussed such topics as the uses of electromagnets, magnetic polarity, magnetic units, and elementary propositions in electro-magnetism. Here we would remark, as a merit in this work, the fact that the author has not loaded what is intended to be a thoroughly practical treatise with long discussions of purely theoretical matters, however important in relation to practice. The sketches of theory given in many works-which are really only collections of tables of numerical data, lists of formulæ, and workshop recipes-would be much better left out, and their places supplied by other matter, or the books lightened by their absence.

An excellent chapter follows, on the properties of iron. The various methods of measuring permeability are well explained, and for the space devoted to it a good account (with tables) is given of the results obtained by Hopkinson and Ewing in their researches. On p. 108 the effect of opening gaps in a magnetic circuit of iron is discussed, and a reference is given to an experiment described later in the work. On turning to this experiment (p. 212), it is found to be a description of an exploration of the effect produced at different parts of a horseshoe steel magnet by pulling off the keeper. A narrow coil of a few turns of wire is wound on a light frame capable of being slided round the magnet, and is connected with a ballistic galvanometer. The effect of pulling off the keeper is then tested with the coil in different positions on the horseshoe, and is shown by the deflection of the needle of the ballistic galvanometer. The theory of the author is, that putting on or taking off the keeper of a permanent steel magnet does not affect the magnetization at the middle of the horseshoe; that by putting on the keeper, and so diminishing the magnetic "reluctance" of the circuit, the lines of magnetic force are only collected, not altered in amount. Hence, if this theory be true, the coil, when placed at the middle of the magnet, should show no effect on the removal of the keeper. It is stated that careful and repeated experiments made at Finsbury gave an effect at the middle of the magnet which did not | amount to 1/3000 of that found when the coil was close up to either end of the magnet.

Some time ago, when informed by a friend of this statement and result, the writer, feeling extremely doubtful of their general truth, had a magnet constructed for the purpose of repeating the experiments. As a large magnet was required for other purposes, one was constructed of eight steel bars of a mean length of about 3 feet. Each bar was 2 inches broad by inch thick, so that when put together they formed a large horseshoe of square crosssection 2 inches in side. A keeper, made of a block of soft iron, fitted between the ends of the horseshoe. The

steel, which was tool steel obtained from a local firm, took magnetism readily, and an excellent horseshoe magnet was obtained.

A coil in circuit with a ballistic galvanometer was used in the manner described above, to test the effect of removing the keeper. Careful experiments made by students, and repeated by the writer, gave an entirely different result from that obtained by Prof. Thompson. A very large throw was obtained by placing the coil close to either end of the magnet and detaching the keeper; but with the coil as nearly as possible at the middle of the horseshoe, the throw was about one-eighth of the maximum. It was verified, moreover, that the minimum throw was obtained at the middle.

This result was exactly what the writer had expected would in general happen. The so-called free magnetism at the extremities of the magnet, in the absence of the keeper, produced a demagnetizing effect throughout the magnet, and thus diminished the induction through the coil, even when at the middle. This action was counteracted by the magnetizing effect of the keeper when in position, and therefore itself inductively magnetized, but had full play as soon as the keeper was removed. The much greater deflections near the ends were undoubtedly due to the cause to which Dr. Thompson would assign the whole effect-the alterations of the arrangement of the lines near the ends which accompanied the removal and replacement of the keeper.

It is certain that this effect will depend on the permeability of the magnet steel, which is a function of the magnetization; but that such an effect will in general be produced there does not seem to be any room for doubt.

The following chapters deal with specially designed electro-magnets, such as, for example, those used in relays and clockwork, electro-magnetic mechanism, alternatecurrent electro-magnets, electro-magnetic motors and machine tools, and the purely electro-magnetic part of the book winds up with a very interesting chapter on the electro-magnet in surgery. The last chapter of all is devoted to permanent magnets. To give a satisfactory account of these chapters is here impossible; but it may be mentioned that the electro-magnetic mechanism fully described and figured includes no less than nine classes, beginning with the different forms of magnet with moving armature or plunger, magnets with armatures moving against counterpoises of different kinds, polarized devices, electro-magnetic vibrators, magnetic brakes, &c.

In chapter xi., on alternate-current electro-magnets, the modes of laminating magnets for the prevention of eddy-currents are described; then follows a discussion of effects of alternating electro-magnets, depending on the difference of the phase relations of the magnets and the eddy-currents excited in conductors in the form of disks and rings placed near the extremities of the iron cores. Thus we have a very interesting account of Elihu Thomson's remarkable experiments. The throttling or impedance effect of electro-magnets included in circuits is next treated. It would have been worth noticing, where the relations of maximum current, maximum electromotive force, mean current, mean electromotive force, and impedance are given, that the true mean value of the total electrical activity in an alternating circuit, in which