study and collection. The Sofia called at Thurso for coal on Sunday and left on Tuesday.

IN connection with Prof. Fries' suggestion of colonising Greenland by mountain Lapps, to which we referred last week, we learn that Baron Nordenskjöld takes with him to Greenland two Lapps from Jockmock, to give their opinion of the country. One of them is thirty, and the other thirty-three years of age.

WE learn from the last annual report of the East Siberian branch of the Russian Geographical Society that this Society, which has contributed so largely to the increase of our knowledge of Siberia, is beginning to recover from the losses it sustained during the great fire at Irkutsk. Private subscriptions have been raised for the reconstitution of the library and museum to the amount of 2170/., and both are in a fair way of development. The library already has about 4000 volumes, but is in great want of foreign geographical publications, and makes an appeal to the geographical ocieties throughout the world to send their publications and, if possible, series of former publications, wh ch ought to be addressed to the Secretary of the East Siberian branch at Irkutsk. The chief occupations of the Society were : the geological exploration east of Lake Baikal, by M. Chersky, who has already published a map of the western coast of the lake; archæological researches as to the prehistoric inhabitants of Siberia, by MM. Agapitoff, Khangaloff, Witkovsky, and Bogolubskiy; and the part it took in the organisation of the Arctic Meteorological Station at the mouth of the Lena, and of a series of four intermediate stations between Irkutsk and this station. This last scheme could not be realised in full, but two stations have already been opened at Verkholensk and at Preobrajenskoye. The last number of the Journal of the Society contains, besides the annual report and the proceedings, a list of new determinations of latitudes and longitudes in Transbaikalia ; a notice on Shamanisur with Yakuts; a paper on the populations of the basin of the Amur, according to Prof. Schrenck; a paper on the inscriptions on stones and rocks in the district of Minusinsk; and several notes, on the Lena Meteorological Station, on the Usuri region, &c.

Petermann's Mittheilungen for May co tains a paper by Mr. Carl Bock describing a journey recently made by him from Bankok to the frontiers of the independent Shan States. He travelled along the Menam River in a boat given him by the Siamese Government, as far as Raheng, where he diverged into the Me Ping. He then proceeded partly by the river, partly by land through Lakon and Lampun, to a town which he calls Tschengmai, but which is more generally known as Kiangmai, or Zimmé. This place, which is the capital of the Shan States tributary to Siam, is an important point in Mr. Colquhoun's proposed railway from Rangoon and Moulmein, into southwestern China. It formed the proposed terminus, too, of that gentleman's recent journey through Yunnan and the Shan States. Mr. Bock described it as a fortified town of about 700,000 people, lying in a fertile plain of uninterrupted rice fields, about 500 yards from the Me Ping, which is here 400 feet wide. Even now it is of great political and commercial importance, as it controls the trade of these regions both with Siam and with British Burmah. The teak forests of the States he describes as almost inexhaustible, especially higher up near the Meikong, where, however, it is not yet known whether the lumber can be easily floated down to the sea. For this purpose Mr. Bock recommends a careful survey of the various rivers and their tributaries. From Zimme he continued his way higher up to Kiangtsen, in the valley of the Meikong, and on the borders of the independent Shan States. It was his original intention to travel through these States into Yunnan, as it was Mr. Colquhoun's to travel through them from Yunnan, southwards. Failing this, he returned to the Me Ping, with the object of tracing this river to its source. He was prevented from carrying out either project by the native hostility, which, we regret to say, Mr. Bock himself did much to intensify, if not arouse, by his indiscreet behaviour. It would be inconceivable, if we did not have it on his own testimony, that any traveller among a people who, as he was specially warned, disliked even the Siamese, and absolutely hated any white man, should so far forget all discretion as to enter a populous town and "out of his own hand," as he describes it, take posses sion of the court of justice, and assault with a stick the official who endeavoured to prevent this unjustifiable trespass. He was punished by several days' imprisonment, but it is unfortunate for the cause of science that the hostility

thus carelessly and wilfully aroused should have put a speedy termination to a journey full of promise. Mr. Bock, however, has shown beyond doubt that a railway from Bankok to the Shan frontiers is a possibility. It would pass through populous and rich districts in the valleys of the Menam and Me Ping. He says that no one who has not visited Zimmé can understand how extensive the trade of the place is, and his proposed railway would place the Laos States in direct communication with the sea, and attract the commerce not only of the Shan States, but also of Yunnan. These are exactly the arguments by which Mr. Colquhoun supports his scheme for a railway to Rangoon. Let us hope that in days to come, when this colossal project is an accomplished fact, there may be no dispute as to the originator of the idea of attracting the trade of south-western China to the sea by means of a railway through the Shan States.

A NEW FORM OF SEISMOGRAPH1

NUMEROUS forms of seismometers have from time to time been invented, and having these various instruments, it may be asked why there is any necessity for a new form, and I can best answer this by quoting from a report of a committee of The British Association of 1872, as follows:-"Some simple and cheap method of indicating earthquake movement is thus much to be desired-any apparatus for the purpose should occupy small space, be little liable to derangement, capable of being put up in any apartment not of special construction, and its indications such as any intelligent person could easily interpret and readily note."

ditions, and hence I bring before you one which is of the very Now none of the instruments yet invented fulfil these consimplest nature.

The idea of the instrument I propose was suggested to me by the a eismatic arrangement designed by my father, Mr. David Stevenson, for averting damage to buildings and lighthouse appara us in countries subject to earthquakes (Trans. Roy. Scot. Soc. Arts. vol. vii.).

The instrument is shown below, and consists of a ground and polished glass plate (A), about 5 inches square, placed level (once for all), on which rest three accurately turned ivory balls about 1 inch diameter, and on the top of these

balls is placed a plate (B) similar to the lower, but having attached to it a projecting arm with a long vertical hole pierced through it. Through this hole passes a steel needle (c) with a fine point, which rests by its own weight on a lampblack surface formed on the plate D. A hair about 2 inches long should be fixed to the eye of the needle to assist in adjusting it. The instrument thus becomes a pendulum of infinite length, so that whenever there is any movement of the ground, and therefore of the lower plates, the top plate with its arm and needle attached remain practically steady, and the point of the needle therefore marks on the lampblack surface the amount of motion and the direction in which the lower plate is moved. This instrument, it will be observed, fulfils all the requirements mentioned in the report of the committee of the British Associa

1 Abstract of paper read before the Royal Scottish Society of Arts, February 13, 1882, by Charles A. Stevenson, C. E., Edinburgh.

organisms found in ordinary and malariac earths, by A. Ceci.Transfusion of blood and its effects on nutrition, by P. Albertoni. -On the pathological anatomy of the cornea in the glaucomatous eye, by F. Tartuferi.-On the presence of a cordon or slip on the Uncus of the Hippocampus in the brain of man and some other animals, by C. Giacomini.—On the chemical composition of the egg and its envelope in the common frog (Rana temporaria), by P. Giacosa.-Anatomical considerations of the doctrine of cerebral localisations, by C. Golgi.

Tome ii. fasc. 3, February 1, 1883, contains anatomical considerations of the doctrine of cerebral localisations, by C. Golgi (continued).-On compensative hypertrophy of the kidney, by C. Golgi.-Experimental studies on hypnotism, by A. Tamburini and G. Seppili.-The origin of the mesoderm and its relations to the vitellus, by G. Romiti.-On the anatomy of a fœtal Otaria (0. jubata), by L. Camerano.-On the physiology of smooth muscular tissue, by A. Capparelli.-On the physiological action of certain substances on the vesical muscles, by P. Pellacani. On the anemia of miners from a parasitological point of view, by E. Perroncito.-On the change in form of uric acid by the action of glycerine, by J. Colasanti.—On Ptomaines, by J. Guareschi and A. Mosso.—On some endoparasitic Protista, by Dr. Grassi.

Tome iii. fasc. i., April 15, 1883, contains:-On the sanitary improvement of the Roman Campagna, by C. Tomma-iCrudeli. On the anemia of miners (conclusion), by E. Perroncito.-On some endoparasitic Protista (conclusion), by Dr. Grassi On the presence of a secretive tissue in vertebrates, by C. Emery.-On vibratile endothelium in mammals, by J. Paladino.-On the attenuation of charbon virus, and on its transmission from mother to foetus, by E. Perroncito.-On the acoustic epithelium, by A. Tafani.-On the termination of nerves in the striated muscles of torpedo, by J. V. Ciaccio.-The general physiology of smooth muscular tissue, by E. Sertoli.On a new morphological element of the blood, and its import. ance in thrombosis and coagulation, by J. Bizzozero.--New studies of the chestnut disease, known as the ink disease, by J. Gibelli.

THE Bulletin de l'Académie Royale des Sciences, des Lettres, et des Beaux-Arts for 1883, part i., contains papers by F. Henrijean, on the part played by alcohol in nutrition; by MM. Valerius and Van der Mensbrugghe, on M. Delaurier's observations on the concentration of solar rays and the transformati ›n of electricity into heat; by W. Spring, on the colour of marine, licustrine, and fluvial waters; by C. Le Paige, on the homo. graphy of the third order in algebra; by Baron Northomb, on the political relations of the Netherlands during the seventeenth century.

SOCIETIES AND ACADEMIES
LONDON

Royal Society, February 1.-"On the Affinities of Thylacoleo." By Prof. Owen, C. B., F.R.S., &c.

Since the communication of the paper "On Thylacoleo," in the Philosophical Transactions for 1871, further explorations of the caves and breccia-fissures in Wellington Valley, New South Wales, have been made, by a grant for that purpose from the Legislature of the Colony, and carried out by E. B. Ramsay, F.L.S., Curator of the Museum of Natural History, Sydney. The present paper treats of the fossils contributing to the further restoration of the great carnivorous Marsupial (Thylacoleo carnifex, Ow.) They exemplify the entire dentition in situ of the upper and lower jaws of a mature individual; the bones of the forelimb, of which those of the antibrachium and the ungual phalanges are described, are compared with those of other Marsupials, and of placental, especially feline, Carnivora. An entire lower jaw with the articular condyles adds to the grounds

for determination of the habits and affinities of the extinct Marsupial.

Figures of these fossils of the natural size accompany the paper.

Geological Society, May 9.-J. W. Hulke, F.R.S., president, in the chair.-Rev. William Spiers and H. A. Williams were elected Fellows of the Society.-The following communications were read :-The age of the newer gneissic rocks of the Northern Highlands, by Mr. C. Callaway, D.Sc., F.G.S., with notes on the lithology of the specimens collected, by Prof. T. G. Bonney, F.R.S. The object of the author was to prove that the eastern gneiss of the Northern Highlands, usually regarded as

of "Lower Silurian" age, was to be placed in the Archæan. While admitting that this gneiss frequently overlies the quartzodolomitic group of Erriboll and Assynt, he held that this relation was due to dislocation accompanied by powerful thrust from the east, which had squeezed both formations into a series of folds, thrown over towards the west, so as to cause a general easterly dip. In Assynt the "Upper Quartzite" was first discussed. The author described several sections which he considered to prove that this band was the ordinary quartzite repeated east of a great fault, which brought up the Hebridean; in one place, Glen Coul, the quartzite being conformably succeeded by the brown flags and dolomite. The "igneous rocks" of Nicol ("Logan Rock" of Dr. Heddle) were regarded as the old gneiss brought up by a fault and thrown over on to the Assynt group to the maximum breadth of more than a mile. The "Upper Limestone" of authors was described as either outliers of the dolomite or a part of the Caledonian series. The "Caledonian" rocks were seen in Glen Coul to be immediately overlying the Hebridean, the Assynt group being caught in the angle between the two gneisses, and bent back in overthrown folds. The mountain groups of Assynt were described as usually consisting of cores of Hebridean gneiss swathed in or capped by sheets of quartzite. In the former case the quartzite on the western slopes was contorted into overthrown folds by the thrust from the east. In the Loch Erriboll district, the " gra. nulite" of Nicol was considered to be a lower division of the Caledonian gneiss, though bearing some resemblances to the Hebridean. In other respects the views of Nicol were regarded as substantially correct. Along the entire length of Loch Erriboll, a distance of about twelve miles, the thrust from the east had bent back the Assynt group into overthrown folds, and pushed the Caledonian gneiss on the top of the inverted quartzite. This had produced the appearance of an "upper" quartzite passing "conformably" below the eastern gneiss. The superior antiquity of the Caledonian was confirmed by the occurrence of outliers of quartzite upon the Arnaboll (Lower Caledonian) series, and by the fact that the granite, which sent numberless veins into the gneiss, never penetrated the quartzite and associated rocks.-On a group of minerals from Lilleshall, Salop, by C. J. Woodward, B.Sc., F.G.S.-Fossil Chilostomatous Bryozoa from Muddy Creek, Victoria, by A. W. Waters, F.G.S.

Chemical Society, May 17.-Dr. W. H. Perkin, president, in the chair.-Capt. W. de W. Abney, F.R.S., delivered a lecture on photographic action studied spectroscopically. The lecturer said he wished that all chemists were photographers; photography occupied the borderland between chemistry and physics; he was firmly convinced that photographic action was interatomic. The action of a developer was then experimentally illustrated; this action is physical. Light causes the liberation of iodine in a film of silver iodide, and the developer precipitates metallic silver. The silver so reduced is infinitesimal, and must be in many cases derived from the film. The positive pole of the electric arc was found to be the best source of light. Gratings could not be used for quantitative work, as they varied so much in their ruling; a glass prism was therefore used to form the spectrum. A film of silver chloride absorbs only the violet end of the spectrum; silver iodide absorbs more, and the bromide most of all; accordingly when a photograph of the spectrum was taken on these three films it was seen that the portion of the chloride acted upon was very much less than

when bromide of silver was used. It was shown that a sensitiser essentially takes up the halogen liberated by the action of light. One salt of silver may act as a sensitiser to another salt of silver. Photographic action is completely prevented by the presence of oxidisers, as bichromate, &c. Reverse photographs were discussed, and the action of sodium sulphite in preventing the evil effects of over exposure. The peculiar green. condition of silver bromide which is sensitive to ultra-red rays was explained. In conclusion the lecturer said that his principal object was to warn chemists of some of the numerous pitfalls which they might encounter in scientific photography.

Meteorological Society, May 16.-Mr. J. K. Laughton, F.R.A.S., president, in the chair.-F. A. Bellamy, T. A. Mercer, Rev. H. J. Poole, and A. Wise, M.D., were elected Fellows of the Society. The following papers were read :Composite portraiture adapted to the reduction of meteorological and other similar observations, by G. M. Whipple, B.Sc., F.R.A.S. It has often been remarked that one of the main, if

not the chief, of the difficulties the meteorologist has to contend with, is the enormous amount of preliminary labour which has to be expended in the not very pleasing task of forming the observations he may wish to discuss into tables, casting the columns of figures so obtained, and then computing the means. With the view of arriving at results by a shorter cut, the author has been led to consider the possibility of employing a method, suggested by a consideration of the highly ingenious system of composite portraiture, invented by Mr. Francis Galton, F.R.S., and utilised in his anthropological studies.—Note on atmospheric pressure during the fall of rain, by H. Sowerby Wallis, F.M.S. The author discusses the condition of atmospheric pressure while rain was falling, during 1882, and finds that, out of a total of 136 rainy days (which were available for his purpose), on 54 per cent. the rain was accompanied by diminishing pressure, on 27 per cent. by increasing pressure, and on 19 per cent. by steady pressure.-New method of reading a thermometer and hygrometer at a distance by means of electricity, by Arthur W. Waters, F.G.S.-An integrating anemometer, by W. F. Stanley, F.M.S.-Observations on the force of the wind at sea, by D.W. Barker, F. M.S.-Meteorological observations at Zanzibar, east coast of Africa, during 1880 and 1881, by Surgeon-Major C. T. Peters, M. B.-Diurnal rainfall at Bangkok, Siam, by Capt. G. H. Inskip, F.R.G. S.

BERLIN

Physiological Society, April 27.-Dr. Mendel read a paper on the anatomy of the corpus striatum and lenticular nucleus. The older view, which was supported by the valuable anatomical researches of Prof. Meynert, was that the relation of the corona of radiating fibres above the lateral ventricle ("Stabkranz") to the lenticular nucleus and corpus striatum consisted in this, that in it ran bundles of nerve-fibres, which arise from the brain cortex and end in the large ganglia, whereas Dr. Wernicke three years ago propounded the view that a connection did not exist between the brain cortex and the corpus striatum and lenticular nucleus, but that these latter were bodies of the same range as the cortex. Dr. Mendel has for some years past studied the anatomy of these parts of the brain very attentively, and has been brought back to the older view by a series of sections (of the brain) of dogs, monkeys, and men, which series he laid before the Society. He found not only the bundles of outstreaming fibres, which alone were acknowledged to exist by Dr. Wernicke, but also a larger number of in-streaming bundles of fibres which show the connection of these brain-nuclei to the cortex. In the discussion Dr. Wernicke stated that he was not convinced by the paper or preparations of the correctness of the view propounded by Dr. Mendel, whereas Prof. Munk believed that his not-yet-completed physiological experiments afford grounds for Dr. Mendel's view.

Physical Society, May 4.-Prof. Hauck laid before the Society a model of a mechanical apparatus which solves the problem of combining drawings and photograms, which are drawn in two planes into a combination figure in the third plane. Prof. Hauck then explained the principle of the apparatus, and pointe 1 out by means of geometrical figures the conditions which must be fulfilled in order to project any given points of two planes in common points of a third plane. He then proceeded to the complicated problem of bringing points of three planes, which meet in a corner, to a common projection, and applied these figures to the special case of projecting the perspective drawing of a building from its ground-plan and elevation. The model was calculated and arranged for this case, but the apparatus, in which the motions are produced by means of polished lineals, each running upon two pins, can be put to manifold uses in physical space investigations.

PARIS

Academy of Sciences, May 14.-M. Blanchard, president, in the chair. The following papers were read: -On the pyroelectricity of quartz, by C. Friedel and J. Curie, second part.On the cultivation of the cacao plant, with an analysis of the constituent elements of the cacao and chocolate berries, which were shown to contain in various proportions albumen, legumine, phosphates, fat, starch, sugar, theobromine, besides the materials entering into the formation of bone.-On the action of birds in flight studied by means of photography, with figures showing the successive positions of a pigeon on the wing at intervals of one-ninth and one-eighth of a second, and a closed curve representing the trajectory of the tip of the wing obtained by means

of a special contrivance, by M. Marey.-On a double sulphate of iridium and potassium, by M. Lecoq de Boishaudran.-On the diminution of virulence in carbon bacterides and their spores under the influence of antiseptic substances, by MM. Chamberland and Roux.-On iodine associated with the sedative alkaloids of opium treated both as a preventative and curative in the case of typhoid fever, by A. Delbovier.-On the immunity against attacks of Phylloxera enjoyed by the vine cultivated in the sandy soil of Algeria, by MM. F. Couvert and L. Degrully.— Observations on the new planet 233 Borelly made at the Paris Observatory, by G. Bigourdan.-On the determination of the meridian in low latitudes, such as that of Rio de Janeiro, by M. Cruls.-On the conservation of energy and periodicity of the solar spots, by A. Duponchel.-On the laws of coincidences between the reductions of periodical fractions of the "two modes," by E. de Jonquières (continued).On the generalisation of Thermat's theorem of numbers due to M. Serret, by M. Picquet.-On the possibility of extending to any electrolytic field the electro chemical method in the figuration of potential distribution, by A. Guébhard.-On the influence of atmospheric pressure on the eruptions of gas and water in the Montrond Geyser (Loire), by F. Laur.-On the differences in the temperature of the sea and air, by M. Semmola. -On the quantitative analysis of sulphur and carbon in sulphocarbonates, by A. Müntz-On the regular surface-fissures in certain rocks, such as the hard eocene limestone used in the construction of the old ramparts of Genoa, by Ch. Contejean.-On new physiological studies of the torpedo, by M. Marey.-On the functions and organs of suction and deglutition in the leech, by G. Carlet.-On a case of purulent ophthalmia produced by the infusion of the seeds of the liquorice plant, by L. de Wecker.On the fundamental principle of the electric log now in use in the French fleet, by M. G. Le Goarant de Tromelin, who claims priority of invention over the electric log invented by M. Fleuriais.

Natural Selection and Natural Theology.-George J.
Romanes, F. R. S.

Carson Footprints.-Prof. Joseph Le Conte.
Cloudiness of Aquarium.-X.; W. Saville Kent
Singing, Speaking, and Stammering.-Alex. Mel-
ville Bell.

On the Cold in March, and Absence of Sunspots.
Dr. C. J. B. Williams, F.R.S.

The Soaring of Birds.-Dr. Hubert Airy
The Zodiacal Light.-E. R. Turner
Sheet Lightning.-Fred. Pratt
Pocky Clouds.-Fred. Pratt

Clerk Maxwell's "Devil on Two Sticks.'
Lane

The Centres of a Triangle.-W. H. H. H.
The Royal Geographical Society

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-Denny

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The True Orbit of the Auroral Meteoroid of November 17, 1882. By Dr. H. J. H. Groneman 105 The Aurora Borealis, II. By Prof. Selim Lemström

Our Astronomical Column:

The Minor Planet, Andromache
The Great Comet of 1882

107

The Flora of Ancient Egypt.

By Dr. G. Schwein

furth (With Illustrations) .

109

On the Chemical Characters of the Venom of
Serpents. By Sir J. Fayrer, F.R.S.
Notes.

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Scientific Serials

Societies and Academies

THURSDAY, JUNE 7, 1883

WIEDEMANN'S “ELECTRICITY"

Die Lehre von der Electricität. Von Gustav Wiedemann. Vol. I., pp. xi. and 795 (1882); Vol. II., pp. vii. and 1002 (1883). (Braunschweig: Vieweg.)

FOR

OR more than twenty years Prof. Wiedemann's "Lehre vom Galvanismus und Elektromagnetismus," first published in 1861, has been recognised without question as the leading authority and great storehouse of facts on the branch of science of which it treats. It is a practically exhaustive treatise, and each of the two editions (second edition, 1872 to 1874) marks with wonderful accuracy the high-water mark of knowledge of its subject up to the date of publication. It is safe to assume that any fact that is not to be found recorded in its pages had not been discovered, or at least had not been published, up to the date of completion of whichever edition is examined. The fulness and accuracy of the references to original authorities give to Prof. Wiedemann's book a unique value also as a classified index to the literature of galvanic electricity and electromagnetism.

The work which forms the subject of this notice, is in one sense a third edition of the "Lehre vom Galvanismus." It appears however under a new title, and is in fact to a great extent a new book. It is characteristic of the direction taken by the advance of electrical science during the last twenty years that, while Prof. Wiedemann found it practicable to confine himself in his first and second editions almost exclusively to the phenomena of current electricity and of magnetism, he has found it advisable in the present edition to enlarge the scope of his work so as to make it include the whole range of electrical science. It is true that the second edition contains an important chapter devoted to the discussion of a phenomenon that has usually been considered in connection with statical electricity, namely, the disruptive discharge in gases of different densities; but this is almost the only part of the book in which the considerations that have to be dealt with in treating of electrostatics occupy a prominent place. It is however becoming less and less possible to treat satisfactorily of one branch of electricity apart from the remainder. The terms frictional electricity and galvanic electricity have evidently an historical rather than a scientific origin. They do not refer to any logical classification of phenomena, but to two among the many processes by which electrical effects can be originated. It is not even by any means certain that electrification by friction is fundamentally a distinct phenomenon from electrification by contact as this occurs in a galvanic cell; on the contrary, various recent investigations tend to show that these actions are essentially similar, and that the friction which takes place in one case is of the nature of an accidental accompaniment. As a matter of fact, however, an electrical machine acting by friction serves (or at least did so until recently) as the readiest means of producing one large class of electrical phenomena; while a galvanic or voltaic battery serves (or at least did so until recently) as the readiest means of producing another large class of phenomena. Thus the division of electrical science for the purposes of study VOL. XXVIII.-No. 710

into frictional electricity and galvanic electricity originated in considerations of experimental convenience rather than in any strictly scientific distinction. So far as such a distinction can be drawn between these two branches, it may be said that the former includes the study of all those phenomena in which difference of potentials is the most characteristic factor; while the latter includes the study of phenomena characterised by the transfer of electricity. As examined by the instruments in use fiveand-twenty years ago, the effects produced by the electrical machine seemed distinct enough from those due to the galvanic battery-indeed the difficulty rather was to establish their mutual connections; but with the galvanometers and electrometers that are now-thanks to Sir William Thomson-in the hands of every electrician, nothing is easier than to measure the current of an electrical machine or the difference of potentials of a galvanic cell. Moreover the recent rapid development of methods of converting mechanical into electrical energy, through the agency of magneto-electric induction, has made us familiar with the production of currents of great strength associated with great differences of potential. It is, however, not only the introduction of new instruments and apparatus, and the increased power over electrical phenomena that modern experimentalists have thereby acquired, that make it less possible now than formerly to treat of the laws of electric currents without reference to the principles of electrostatics. The conception that the immediate cause of the phenomena exhibited in either an electric or a magnetic field has its seat, not in electrified conductors, or in magnets or conducting wires, but in an impalpable medium existing throughout space, has completely shifted the scientific point of view as regards electrical effects. What is now demanded of electrical theory is an explanation of the conditions of the medium which are perceptible by us as the properties of an electric or magnetic field. The wider problem of the constitution of the electric medium, whether identical or not with the luminiferous ether, embraces in itself the phenomena of electrostatics, of electric currents, and of magnetism.

There was thus every reason to wish that Prof. Wiedemann might be able to treat electrical science as a whole in the same complete way in which he had previously treated the portions included within the scope of his previous book. This is what he has now undertaken and in great part accomplished. The task is an enormous one, and probably, to any one except the man who has set himself to it, would have seemed overwhelming. Prof. Wiedemann's industry and care, however, never seem to fail before any mass of descriptive detail or complex mathematical discussion, and students of physics may therefore be congratulated upon the near prospect of having from his pen a complete treatise on electricity.

The first of the two volumes already published begins with a section on the General Properties of Electricity, including an historical sketch of early observations, the development of electricity by friction, &c., electrostatic attraction and repulsion, distribution on conductors, and a description of the various forms of electroscopes and electrometers. Then follows a section on the development of electricity by contact of heterogeneous bodies; next Ohm's law and its applications, the measurement of electrical resistance and of electromotive force, and a

G