the observational and experimental work of the Observatory. The curves of the magnetographs have shown a marked increased activity in terrestrial magnetic changes as compared with the previous year, although no very large disturbances have been registered. The electrograph has been maintained in action during the greater portion of the year, but the instrument has failed in sensibility, owing to the diminished potential of the chloride of silver battery. The subject of the measurement of atmospherical electricity is consequently far from settlement. Sketches of sun-spots were made on 170 days, and the groups numbered after Schwabe's method. Two new forms of anemometer have been under trial: (1) the anemo-cinemograph of MM. Richard Frères, similar to that employed at the top of the Eiffel Tower-the vanes, by running constantly against a train of clock-work, record directly on a sheet of paper the velocity of the wind at any moment; (2) the Munro sight-indicating anemometer is a sensitive Robinson cup arrangement, which drives, by means of a small centrifugal pump, a column of oil up a glass tube. The instrument, as fitted at present, fails to work during frost, owing to congelation of the oil employed. Great activity continues to be shown in the verification department, over 20,500 instruments of all kinds having been tested; more than three-fourths of these were clinical thermometers. In the rating of watches, the highest position was attained by Messrs. Stauffer, Son, and Co., one of whose watches obtained a total of 916 marks out of a possible 100. Special circulars have been addressed to the directors of steamship companies, calling attention to arrangements made for the rating of chronometers. A special camera, capable of working with lenses of 4 inches aperture and 30 inches focal length, has been fitted up at the Observatory, for the examination of photographic lenses. A photometer, on Captain Abney's principle, 13 feet long, has also been fitted for use in the testing operations. The Committee have come to the conclusion that it would be of advantage to them to obtain registration under Section 23 of the Companies Act, 1867.

WE have received from the Deutsche Seewarte, (1) the Deutsches meteorologisches Jahrbuch for 1890, containing observations taken three times daily at nine stations of the second order, with monthly and yearly results, hourly observations and means at Hamburg and Wustrow, and extracts from the registers kept at the signal stations, on stormy days. The materials are similar to those published in former years, the only change being in the reduction of the number of stations for which observations from self-registering instruments are given. (2) Ergebnisse der meteorologischen Beobachtungen for the lustrum 1886-90, on the same plan as those previously published for the years 1876-80 and 1881-85. These publications extend over fifteen years, and form a very valuable contribution to the climatology of Northern Germany, affording ample data for investigations referring to individual hours, or days, together with an easy means of obtaining the combined results and the extreme values for the whole period over which the observations extend.

THE Washington Weather Bureau has just issued an atlas of thirty-six charts, being one of a series of useful works partially prepared under the superintendence of General A. W. Greely, Chief Signal Officer of the United States, prior to the transfer of the Meteorological Service. The charts show the average direction and hourly velocity of the wind at 8 a.m. and 8 p.m. (Washington time), at sixty-five representative stations, with the average maximum and minimum hourly velocity, and other interesting details, from observations for a number of years. The prevailing wind direction, and the direction next in order of frequency, are shown by arrows which fly with the wind, while figures set against the arrows indicate the percentage of

times the wind has been observed in the direction indicated by the arrows. General Greely remarks that the diurnal variation of the wind in the United States has not been investigated to any considerable extent, so that but little is known of its tendency except in a general way. It may be said, however, that in the northern hemisphere there is a well-defined tendency to veer a little in the morning, and to back through the same circumference in the afternoon. This inclination, however, is early subordinated to the influence of pressure changes and distribution, and cannot be detected except in settled weather.

WRITING in the American journal Electricity, on electricity in the United States Navy, Mr. W. B. Lefroy Hamilton refers to the working of the search light. He says that in

the practical use of the search light, it has been found that in order to afford sufficient time for a careful exami

nation of the water's surface, at points far removed from the ship, the beam of light must be revolved very slowly, and in consequence, during a great portion of the time any particular section of water is left in darkness. As it only takes five minutes for a torpedo boat to run a distance of two miles, it will be easily seen that in the interval between two successive illuminations of the same spot, a torpedo might attack a warship and discharge her deadly weapon. To overcome this difficulty, it is proposed that the new American war-ships, beginning with the New York, shall be fitted with a number of stationary search lights grouped together, each illuminating its own section, thus keeping the ship surrounded by an unbroken circle of light.

THE leather industry is to have a separate building at the Chicago Exhibition. Representatives of the industry have accepted a site offered them, and will erect, at an expense of 100,000 dollars, a building, measuring 150 by 600 feet, in which they will show an almost endless array of leather products, and every process in their manufacture from the raw hide to the most finished article.

THE latest annual report of the Hon. Edgar Dewdney, Superintendent of Indian Affairs in Canada, gives much interesting information as to the aborigines of the Dominion. They are dis tributed thus :-Ontario, 17,915; Quebec, 13,361; Nova Scotia, 2076; New Brunswick, 1521; Prince Edward Island, 314; Manitoba and North-West Territories, 25, 195; Peace River district, 2038; Athabasca district, 8000; Mackenzie River district, 7000; Eastern Rupert's Land, 4016; Canadian Labrador, 1000; Arctic coast, 4000; British Columbia, 35, 202 total, 121,638. The number of children of school age is 13,420, of whom 7574 are in attendance. Even in the NorthWest, where the conditions are harder than in British Columbia, great progress has been made. The property owned by the Manitoban and North-Western Indians includes 5599 houses and 2018 barns; 13,549 acres of land under cultivation, with 2115 acres newly broken; 1251 ploughs, 773 harrows, 899 waggons, 48 fanning mills, and 5 threshing mills; 2928 cows, 70 bulls, 2064 oxen, 4823 calves, 5879 horses, 428 sheep, and 215 pigs. Last year the North-Western Indians reaped a harvest including 67,726 bushels of wheat, 21,592 of oats, 19,761 of barley, 44,284 of potatoes, 14,788 of turnips, 1340 of carrots, and 413 of rye. The farm instructors and their wives make a point of teaching the Indians how to use their spare time. The men are encouraged to make handles for axes and hay forks, besides sleighs, ox collars, harness, brooms, &c. The women are initiated in tanning and butter-making, and already make articles of clothing that would not disgrace a white woman, being particularly quick at knitting; some of them, too, are expert in the manufacture of baskets, mats, and hats. The housing of the people also improves, the Bloods in particular now partitioning their houses into rooms. The trust funds held for the Indians by the Government now amount to £703,046, and £57,098 was spent from this source last year, besides £186,442 voted by

Parliament. Of the Parliamentary grant no less than £164,437 went to the North-West, including Manitoba and Keewatin; while British Columbia took 17,010 of the remainder.

THERE seems to be no doubt that the aborigines of the Andaman Islands are rapidly disappearing. According to the latest administrative report relating to the islands, all the people of Rutland Island and Port Campbell are dead, and few remain in the South Andamans. Mr. Portman thinks that the present generation of this interesting race will be the last. Only a small number of children are born, and they do not survive infancy.

IN his Presidential address to the American National Geo graphic Society, now printed in the Society's Magazine, Mr. Gardiner G. Hubbard presents an interesting sketch of the forces which have been at work in the evolution of commerce. In the concluding passage he glances at what he supposes to be the future of commerce. America, the last of the continents to be inhabitated, now receives, he points out, the wealth of Asia on the one hand and manufactures and population from Europe on the other. "Here the East and West, different from each other in mental power and civilization, will meet, each alone incomplete, each essential to the fullest and most symmetrical development of the other. Here will be the great banking and commercial houses of the world, the centre of business, wealth, and population."

IN ancient times Greece possessed something like seven and a half millions of acres of dense forest, and she was comparatively rich in timber until half a century ago. Many forests have now disappeared, and the result is seen both in the scarcity of the water supply and in various injurious climatic effects. The Austro-Hungarian Consul at Athens-while calling attention to these facts in a recent report, of which some account is given in the Board of Trade Journal for April-points out that even at the present day Greece possesses about two millions of acres of forest land. The quantities (in cubic metres) of timber and forest produce obtained in 1890, compared with 1889, were : building wood, 59,948 and 48,986; timber for shipbuilding, 2606 and 1640; for tools and machinery, 4146 and 2940; lignite, 509,895 metric centners, compared with 466,953; asbestos, 491,722 metric centners, compared with 490, 179; and tanners' tawing materials, 20,003 metric centners, compared with 30,089 in 1889. Notwithstanding this considerable production, Greece will have to import large quantities of timber in the near future, so as to meet the demand arising from the revival of the building trades now affecting both the rural and urban districts of the peninsula.

A PAPER on the agricultural needs of India, by Dr. J. Augustus Voelcker, was read the other evening before the Society of Arts, and is printed in the current number of the Society's Journal. It gave rise to an instructive discussion, in the course of which Mr. Thiselton Dyer-referring to the necessity of India producing sufficient food for its growing population-said the real question was how to get more nitrogen into the soil. That overshadowed everything else. He agreed with Prof. Wallace, who had spoken before him, as to one way of supplying this want. After the studies made in Germany, France, and England, there could be no longer any doubt that the growing of leguminous crops did enrich the soil with nitrogen in a way which, as far as was at present known, without manure, could be done in no other way; but in India the method of green soiling was not altogether unknown. If it were, the sooner some popular account of the method was distributed the better. An old pupil of his own, who had charge for a time of an experimental farm at Bangalore, found that by making some slight addition to the Indian plough he was able to stir the soil-not to plough

deeply, but to stir it lower than the ordinary plough did, and, by slightly opening the subsoil in this way, the roots were able to get down lower, and the crops, even in a season of drought, flourished in a way they did not when the soil was cultivated in the ordinary manner. He was inclined to think that the Indian could not be studied very well by people in Europe, because our plough was a thing which deserved a good deal of study; but it conditions were so different. The study should be made on the spot, and efforts should be made to improve the agricultural methods there by the introduction, if possible, of some kind of rotation with leguminous crops. He was under the impression that, in a great deal of the cultivated land of India, there was something like a pan, formed at no great distance below the surface, which made it extremely difficult for the roots to penetrate, and so they were unable to bear even a slight drought.

THE Great Bower Bird seems to give the people of Northern Queensland very frequent occasion to think about him. Every kind of fruit suffers from his depredations; and, according to a letter from Mr. E. M. Cornwall, printed in the Victoria Naturalist, he has also a taste for new-laid eggs. Says Mr. Cornwall :-"This is not mere supposition, but hard fact, for after noticing the disappearance of eggs in a most unaccountable manner for some time, the gardener kept watch, and was rewarded by seeing Mr. Bower Bird fly straight to a nest just vacated by a hen and deliberately pick the egg and polish off its contents." "In re the Great Bower Bird.-Since writing you last, I have had still further evidence to convict this rogue of what I charged him with. A bird was seen to fly right to a hen's nest in an empty shed and immediately emerge with an egg in his long claws; but the egg proved an awkward burden, and he dropped it ere he had gone many yards."

COLONEL W. S. HORE gives in the journal of the Bombay Natural History Society (vol. vi., No. 3) an interesting account of the taming of a heron. Writing from Deesa in September 1891, he says that during the then recent monsoon a young egret or heron with a greenish-brown neck and body, white-tipped wings, and green legs, flew into the verandah of his house, apparently in search of food. He caught it, and for about ten days kept it under a large basket, feeding it with raw meat. He then gave it its liberty, but it refused to leave. It grew very tame, and would feed out of Colonel Hore's hand. Occasionally it would indulge in a bath in one of the dog's tins, and afterwards sit on a chair in the verandah. In the evening it flew away to roost in one of the large neem trees in the compound. It showed no fear of the dogs, and would give any of them who came too near a vigorous "dig" with its long bill. It remained with Colonel Hore for about six weeks, when, as his regiment was under orders to march, and he was afraid if left behind it would meet with an untimely end, he carried it down to the river about two miles off and left it there.

THE new number of Petermann's Mitteilungen has a map of the Kalahari Desert, and the western part of British Bechuanaland, with remarks by Edward Wilkinson. There are also articles on the Pamir question (with map), by F. Immanuel, and contributions to our knowledge of the south-eastern part of Persia, by A. J. Ceyp.

THE Rochester Academy of Science, U.S., has published two brochures of the first volume of its Proceedings. The papers are attractively printed and well illustrated. Among the contributions we may note "The Aurora," "The Forces concerned in the Development of Storms," and "The Zodiacal Light," by M. A. Veeder; " Description of New Meteorites," and "Notice of a New Meteorite from Louisa County, Va.," by Edwin E. Howell; "Root Foods of the Seneca Indians," by G. H. Harris; "Descriptions of New Species of Muricide, with remarks on the apices of certain forms," by Frank C.

Baker; and "Notes on Mexican Archeology," by F. W. Warner.

MESSRS. WM. BLACKWOOD AND SONS will publish, in the course of a few days, a short treatise on Farmyard Manure," by Mr. C. M. Aikman, Lecturer on Agricultural Chemistry, West of Scotland Technical College.

MESSRS. SMITH, ELDER, AND CO. have issued a third edition of the "Junior Course of Practical Zoology," by Prof. A. Milnes Marshall, assisted by Dr. C. Herbert Hurst. Advantage has been freely taken of corrections and suggestions received from many sources. The whole book has been carefully revised, and some new figures have been added.

THE Royal University of Ireland has issued a supplement to its Calendar for the year 1892. It includes the examination papers used in 1891.

acid have been prepared. They are all red or brownish-red solid substances possessing properties similar to those of titanium phenylate.

THE additions to the Zoological Society's Gardens during the past week include a Grivet Monkey (Cercopithecus griseoviridis) from North-east Africa, presented by Miss G. A. Vicars; a Leopard (Felis pardus 8) from Ceylon, presented by Mr. Marcus W. Millett; a Lesser Sulphur-crested Cockatoo (Cacatua sulphurea) from Moluccas, presented by Mrs. Kate Taylor; a Greater Sulphur-crested Cockatoo (Cacatua galerita) from Australia, presented by Mr. Earle Whitcombe; a Common Zebra (Equus zebra 9) from South Africa, a Wonga-wonga Pigeon (Leucosarcia picata ?) from New South Wales, a Cereopsis Goose (Cereopsis nova-hollandia) from Australia, deposited; a Yak (Poëphagus grunniens 8), born in the Gardens.

tion TiO(CH), or Ti(C ̧H2O) ̧. The discovery of these somewhat remarkable compounds was the result of an investigation concerning a colour reaction of titanic acid. M. Lévy had observed that when a small quantity of titanic acid was brought into contact with sulphuric acid containing a little phenol, a deep red coloration was produced. The red colouring matter was soluble in the oil of vitriol, but was decomposed when the solution was diluted with water or neutralized by alkalies. The red substance has, however, been isolated by employing another mode of preparation, and proves to be the titanium phenylate, Ti(CHO), above mentioned. It may readily be prepared by the action of titanium tetrachloride, TiCl, upon a solution of phenol in benzene. The titanium tetrachloride, in quantity one molecular equivalent, is poured directly into the solution of four molecular equivalents of phenol, when a very energetic action occurs with liberation of a large quantity of hydrochloric acid gas. The last traces of hydrochloric acid are removed by means of a current of hydrogen, the reaction flask being warmed to about 70° by means of a water-bath and fitted with a reflux condenser. Upon the completion of the reaction the benzene is evaporated off, when the new compound is left behind in the form of large crystals. The crude substance thus prepared is then recrystallized from a mixture of benzene and petroleum, when it is obtained in the form of rhombohedral crystals of the colour of bichromate of potash, and which, like the latter compound, yield a powder much yellower in colour upon pulverization. The crystals are readily soluble in benzene, toluene, alcohol, or ether. They also dissolve in concentrated sulphuric acid, producing the same red oil which is formed in the colour reaction above described. The action of water upon the crystals of titanium phenylate appears to be of the nature of saponification. It occurs in at least two stages, a compound TiOH(CH) being first produced; this intermediate compound passes eventually into titanic acid, carbolic acid being at the same time formed in the solution. Fuming nitric acid, when in large excess, converts titanium phenylate into titanic and picric acids; but if only a small quantity of nitric acid is employed, titanium picrate is precipitated in the form of a black insoluble substance. Nascent hydrogen, liberated by means of dilute hydrochloric acid and zinc or tin, reduces the titanium in titanium phenylate to titanium trichloride, with production of the usual violet coloration due to that compound. Gaseous chlorine rapidly converts the crystals of titanium phenylate into titanium tetrachloride and the di-chlorine derivative of phenol. addition to titanium phenylate, the analogous compounds with the cresol phenols, thymol, naphthol, resorcinol, and salicylic

In

OUR ASTRONOMICAL COLUMN. ASTRONOMY AT THE PARIS ACADEMY, APRIL 11.-MM. Périgaud and Boquet have independently made some observathe investigation being to determine whether the value underwent a periodic variation. The two series of observations only differ from one another by about one-hundredth of a second of arc; the value derived from them is 48° 50' 11" 01. No definite evidence of variability was obtained. Admiral Mouchez, in commenting upon these observations and a discussion of the latitude of the Observatory, made by M. Guillot in 1879, said that doubtless the variation found at other Observatories was wholly or in large part due to the influence of temperature on astronomical refraction. A photograph taken by Dr. Gill was presented by Admiral Mouchez to the Academy. It embraced an area of 2° x 2°, and on this skyspace from 30,000 to 40,000 stars had left their impressions, besides two nebulæ. The exposure given was 3h. 12m. instead of the 1h. which is given to plates for the "Carte du Ciel." If this exposure were possible for the whole photographic map of the heavens, about 300,000,000 stars would record their existence instead of 30,000,000.

Swift's and Denning's comets have been observed at Bordeaux on several occasions. The former is described as very brilliant, with a nucleus of about the seventh or eighth magnitude, a head compared the calculated time of eclipses of Jupiter's satellites about 8' in diameter, and the trace of a tail. M. Landerer has given in the Connaissance des Temps with the actual times observed. The agreement between the two is very remarkable. SOLAR HEAT.-Volume ii. of the Transactions of the Astronomical and Physical Society of Toronto (1891) has recently been issued. It contains several interesting papers, one of Two which, by Dr. Joseph Morrison, deals with solar heat. theories have been advanced to account for the source and maintenance of the heat of the sun. One ascribes the heat to the energy of meteoritic matter falling on the sun, the other asserts that the supply of heat is kept up by the slow contraction of the sun's bulk. Taking the "solar constant as twenty-five calories per square metre per minute, Dr. Morrison calculates that the linear contraction of the radius of the sun which is requisite to keep up the present rate of radiation, is o'000004972 feet in I second, or 1569 feet in a year, or 29.716 miles in a thousand years. "Now 450 miles of the sun's diameter subtends at the earth an angle of 1", and therefore it would require 7575 years for the sun's angular diameter to be reduced by I" of arc, which is the smallest angle that can be accurately measured on the solar disk. With regard to the meteoritic theory of solar energy, a calculation shows that a quantity of matter which weighs one pound falling freely from infinity to the sun would develop by its kinetic energy 82,340,000 units of heat. From this it can be found that the heat radiated could be developed by the annual impact on the sun of a quantity of meteoritic matter a trifle greater than 1/100th of the earth's mass, and having a velocity of 382.6 miles per second.

PERIODIC VARIATIONS IN LATITUDE.-Mr. Chandler, in some recent numbers (248 and 249) of the Astronomical Journal, announced the discovery that the earth's axis of rotation revolves round her axis of maximum moment of inertia in a period of

about 427 days. In the Monthly Notices for March, Prof. Newcomb contributes a paper on the "Dynamics of the Earth's Rotation," in which this result is mentioned with reference to the periodic variations in latitude. By dynamic principles the ratio of such a rotation to that of the earth's revolution "should be equal to the ratio of her polar moment of inertia to the difference between the equatorial and polar moments." This gives a time of rotation of 306 days. Mr. Chandler's result, as Prof. Newcomb says, "at first sight seems in complete contradiction to these principles," and he is led to inquire into the theory which assigns the time of rotation. The present paper is the result of such an investigation, and he finds that two defects have made themselves apparent-"namely, the failure to take account of the elasticity of the earth itself, and of the mobility of the ocean." If the earth be considered first of all to be rotating as a homogeneous spheroid covered by an ocean of the same density as itself, the axes of rotation and figure would of course be perfectly coincident. By supposing a slight displacement of the axis of rotation of o" 20 in the case of our earth, he estimates approximately one-fourteenth of this as the movement of the axis of figure in consequence of the shifting of the ocean. As twosevenths are required by Mr. Chandler's results, "the ocean displacement only accounts for one-fourth of the difference." Since the remainder must be attributed to the elasticity of the earth, he inquires into the rigidity that our planet must have, so that the displacement of the axis of figure may be two-sevenths that of the axis of rotation: the result of the inquiry is to find that a rigidity greater than that of steel must be assigned to it. The effect of viscosity, he mentions, makes the normal pole move slowly and continuously towards the revolving one, so that in time they would meet if they were not acted upon occasionally by some opposing forces. The pole of rotation, according to Chandler's period, makes six revolutions in seven years, and Prof. Newcomb investigates the effect of an "annually repeated cause that might produce such a change in the position of the earth's axis. This effect, as he points out, would be cumulative for onehalf the period of seven years, and as the displacement is small, a comparatively minute disturbing force can be looked for. Basing his calculations on Chandler's period, he finds that such an effect can be obtained, for, "if the winters in Siberia and in North America occurred at opposite seasons, we should have no difficulty in accepting the sufficiency of annual falls of snow to account for this anomaly."

RECENT ADVANCES IN PHYSICAL CHEMISTRY1

its course of development from a descriptive into a rational IN science, chemistry has, in a tolerably regular series of changes, passed in turn through periods of more special and of more general interest. While the gathering together of empirical facts proceeds in quiet, steady work, little troubled by minor and rapidly decided differences of opinion, it is regularly noticed, upon the other hand, that more generalizing ideas, brought forward for the purpose of a rational comprehension and unifying of this material, obtain only in the rarest cases a kindly, immediate reception. On the contrary, the reaction which such things at first call forth is almost always a more or less violent opposition, its precipitate is to be sought out upon the filter of the scientific literature of the time, there coming afterwards to our view, in the text-books, only the clear filtrate of the pure results. This has scarcely ever appeared more strikingly than in the fall of the phlogiston theory: the periodicals and books of the last century resound again with the strife of the opponents, and often enough were the moral qualities of the newer party attacked when the opposed arguments became threadbare; whereupon from the attacked party a corresponding reply was never lacking. The intellectual combat died away but slowly, until the new territory was occupied in common in peace and harmony. We have lived through a similar experience in the change from the electro-chemical theory to the substitution-theory, in the transfer from the idea of equivalents to that of molecular quantities, in the transformation of the radical theory into the theory of types and structure. Even the younger men among us remember the strong opposition with which was greeted at its first appearance that idea of the

1 Address delivered before the united Sections of Physics and Chemistry at the yearly meeting of German Men of Science and Physicians at Halle, September 24, 1891, by Prof. W. Ostwald, Ph.D., of Leipzig.

arrangement in space of the atoms in molecules, which now occupies so many investigators.

So it is a bloody field, whose present condition I have undertaken to represent to you to-day. Do not fear that I shall bring the uproar of conflict into this hour of peaceful looking backward and forward. I have rather called up these recollections in order to awaken in you the consciousness that this strife, which has indeed not been wanting in the more recent years of the development of general chemistry, is no abnormal phenomenon, possibly called forth by an unusual inferiority of the newly appearing general ideas or of their defenders, but that it is only a question of the normal birth-pains which unavoidably accompany the appearance of important generalizations. But before taking up connectedly these newer and newest things, it will be in place to cast a glance over the development of those fields whose progress has been of a steady nature.

First, as concerns the atomic weights. The investigations which have been carried on for some years by American and English investigators-Cooke and Richards, Morley, Lord Rayleigh, Noyes, Dittmar, and others-upon the relation be tween hydrogen and oxygen, have not yet been brought to a close. While most of the determinations have united to indicate that the ratio of the atomic weights of these elements is I to 1587, thus differing about o 8 per cent. from the previously assumed value I to 16.00, yet by means of a well-thought-out method, Kaiser has found first 15'945, while he has now just announced that the most probable value is the old I to 1600. It is remarkable that the efforts of so many investigators to determine this fundamental constant accurately to within one part per thousand have not yet met with a generally-accepted success.

In this connection are to be mentioned the discussions, which have been held upon the question as to the practical unit for the atomic weights, whether O=16'00 or 15'96 should be employed. This is not the place to test the grounds adduced on both sides. Perhaps it may be possible, with the present stricter organiza. tion of cur Society, to form a commission which shall subject the question to a general examination, and which, by the standing of its members, shall be endowed with sufficient authority to insure to its decision some prospect of general acceptance.

The question as to the connection and significance of the numerical values of the atomic weights has made no progress of importance since the fundamental researches of Lothar Meyer and Mendeleeff. Indeed, speculations do not cease in the direction given by the assumption of a compound nature of the elements, yet I know of none for which I could dare prophesy growth and development. Steady work in the revision of the numerical values of the atomic weights has been patiently prosecuted. I need mention especially only the close of the researches of the untiring Seubert upon the metals of the platinum group; and we should recognize with great thankfulness the devotion with which this work, so thankless in itself, has been carried through.

No new elements of importance have come recently to light. Although in the garden of the "rare earths" many a blossom has appeared, there fail as yet any real fruits.

In the theory of gases the investigations continue according to the general equation of condition (Zustandsgleichung), in that the recognition is steadily breaking its way, that the nearest entrance to the theory of liquids leads necessarily over the critical point. The kinetic hypothesis, which was greeted in its time with so much sympathy, and has enjoyed such careful attention, is showing itself here essentially unfruitful, since the two main principles of the theory of van der Waals, to which the immediate future undoubtedly belongs, are independent of the kinetic hypothesis. In fact, neither the assumption that only the space which is not filled with the substance of matter follows Boyle's law, nor the assumption that this matter possesses still some energy of reciprocal action, necessitates any definite representations whatever in the sense of the kinetic hypothesis.

Among the experimental researches upon these relations are especially to be mentioned those of Ramsay and Young. The relation determined by them, that within a very wide range the equation (v - b) = ƒT is true, or that the co-volume, b, is independent of the pressure, is one of the few general facts which are leading us to a more accurate knowledge of the general equation of condition.

In solving the task of finding a theory of the liquid condition, we shall have to seek other properties, which show themselves to be here subject to the more simple laws. As yet but few

such have become known, and still fewer have been considered in this manner. In addition to the above-mentioned result of Ramsay and Young, there claims attention one discovered by the Hungarian physicist Eötvös, according to which the molecular surface energy, as expressed by the product of the capillary constant and the 3rd power of the molecular volume, is shown to be a linear function of the temperature. Since the surface energy

stands in closest connection with the energy of interaction, by virtue of which the substance of liquids, in contrast to that of gases, assumes its own proper volume, and to which is accordingly due the characteristic existence of the liquid condition, it becomes at once evident that here certainly a means of access to the theory of the latter is afforded. This means may be expected to lead more rapidly to the goal than the methods hitherto almost exclusively tried, based upon a relation between volume, temperature, and pressure.

The stöchiometry of the liquid organic compounds, founded by Hermann Kopp, has enjoyed likewise a steady development. While the question of the boiling-point seems to be essentially postponed until the general theory of liquids becomes known, yet that of the molecular volumes has reached a stage which already assures the prospect of a successful period of development. The additive scheme, proposed by Kopp as a first approximation, according to which the molecular volume is the sum of the atomic volumes-a scheme whose insufficiency Kopp himself had shown in the case of oxygen-determines only the roughest outlines of the phenomenon in question. Other factors make themselves everywhere felt; as was shown by Kopp for oxygen-that the portion of the molecular volume due to it can assume different values according to the function of this element in the compound, i.e. according to the constitution of the molecule-so the same holds for the other elements. An essential difference between univalent and bivalent elements is, in this respect, not present: ethylene and ethylidene chlorides have different molecular volumes, although they both contain saturated carbon atoms, and, in addition, only univalent elements.

We must, accordingly, more than ever before, recognize the molecular volume as a constitutive property. This recognition removes at once the firm barrier to which the additive scheme, greatly against the will of its originator, had hardened. In vain had been for so long striven to force the facts into this form; ever and again their living body would not fit upon the wooden cross. Now we see that this undertaking was necessarily in vain we begin to comprehend that methyl alcohol must be more different from ethyl alcohol than ethyl alcohol from propyl alcohol; and that these two, again, must stand in a different relation than do propyl alcohol and butyl alcohol, although each time the " same "difference of CH, is at hand-that there are, in short, no two pairs of compounds whose differences are entirely

the same.

Now, it is quite dependent upon the nature of the property considered, in what relation the additive foundation stands with the modifying effect of constitution. With the molecular volume the first is comparatively superior; with the boiling points, however, the latter make themselves to the most superficial observation so energetically felt that, since the attempts of Schröder, Löwig, and others, which over fifty years ago failed to carry through the additive scheme for the boiling-points of organic compounds, this line of effort has been definitely given up. The other properties which have been studied fall between these two limits.

This holds especially for the molecular refraction. Just as Buff had earlier shown that "double bound" carbon possesses a greater molecular volume than does saturated carbon, it has been demonstrated by Brühl that a similar relation holds for the molecular refraction. This influence of constitution is, however, not the only one; a similar inference has been shown for oxygen and likewise for chlorine, and it has been repeatedly shown that, even if approximately additive laws be followed among the higher members of homologous series, yet these do not apply for the first members. This is necessarily so, as has already been shown in discussing molecular volumes.

The magnetic rotation is a property of much more strongly marked constitutive character than are molecular volume and molecular refraction. We possess here most excellent investigations by Perkin, which have often been found of service in determining questions of constitution.

In relation to the connection between the different properties of substances a fruitful line of thought has been carried out by Philippe-Guye. As is known, Maxwell had derived a definite

relation between the coefficient of refraction and the dielectric constant, from his wide-reaching speculative investigations, which latter had yielded a complete analogy of the mathematical expressions for electrodynamical and optical action at a distance, together with an approximate equality of the fundamental constants, and which have been finally made fruitful by the brilliant experimental investigations of Hertz. This dielectric constant is in turn, according to an expression due to Clausius, a simple function of that fraction of the total volume of a dielectric which is occupied by the actual material substance (considered as conducting). But this so called true molecular volume is, finally, nothing but the co-volume in the equation of Van der Waals. There is accordingly to be expected a close connection between the critical constants and the molecular refraction, and Guye has shown that the expected connection actually exists.

Although spectrum analysis, with its manifold applications, has for years had almost no rational development, it has recently taken a quite promising start in the stöchiometric direction. The theoretical and experimental researches of Balmer, Deslandres, Julius, Rydberg, Kayser and Runge, and others, indicate already that the time is not far distant when there shall be simple and intelligible regularities in this field, which until now has been so overgrown with unfruitful hypotheses. Only upon one point I wish at this opportunity, as a chemist, to direct the attention of the physicists. It is held as an undoubted dogma that at the highest temperatures, as, for example, in the electric light arc, all compounds must be dissociated into their elements. This view is certainly not justified. What we do know about the stability of compounds is, on the contrary, that all compounds which are formed with absorption of heat become more stable with rising temperature, and the reverse. Because the majority of the compounds known to us are formed from the elements with evolution of heat, and correspondingly become more unstable with rising temperature, the conclusion has been drawn that this is in general the case. But if we reflect that cyanogen and acetylene, two compounds formed with great absorption of energy, are readily formed in quantity, at the highest temperatures, in the blast furnace and in the Davy arc light, we become conscious that the spectra occurring at high temperatures may, under proper conditions, belong to compounds which, formedu with great absorption of energy, may have a fleeting existence confined to those temperatures only. From this point of view, many difficult facts of spectroscopy and spectrometry would have some prospect of a proper interpretation.

At the extreme boundary of the optical properties, towards the side of the constitutive character, stand finally colour and rotation of the plane of polarized light. Although the first property is decisive for one of the most important branches of technical chemistry, the dye-stuff industry, still but little is known as yet about the connection of colour with composition and constitution. The investigations of Krüss, Liebermann, and more recently Vogel, all indicate that the property is in great measure constitutive, becoming additive only within the narrowest limits of closely-related compounds. This renders correspondingly difficult a recognition of the connections at hand. Some time later, on the contrary, directly on account of this marked constitutive character, the colour will be an important aid in the determination of constitution; at the same time, when we shall have learned to recognize this connection with some certainty, the discovery of new dyes with definite properties will be no longer a matter of a lucky hand and of an unconscious feeling for this connection, but will rest upon just as broad a basis as, for example, the technic of the metallurgical processes.

The constitutive character of the rotation of the plane of polarization has been always known and recognized. Since van 't Hoff and Le Bel, twelve years ago, pointed out the connection between this property and the presence of an " asymmetrical' carbon atom, i.e. one joined with four different elements or groups, this idea has, at first slowly, then more and more rapidly, had an important development. For the "optical symmetry" shown by Pasteur in the tartaric acids, the examples have become more and more numerous; the researches of Wallach on the ethereal oils have especially furnished valuable material. The presence of optical activity is now held as an entirely undoubted proof for the presence of asymmetrical carbon, and Le Bel has just announced that he has succeeded in the preparation of optically active nitrogen compounds containing an asymmetrical nitrogen atom.

The investigator whom we have already mentioned, Philippe