from the furnaces. In a third case, a mixture of metallic nickel, steel, and cast iron, containing about 20 per cent of nickel, covered with a layer of flux, had been melted in a graphite crucible. When the crucible was removed from the furnace and the cover removed, there rose up a sheaf of sparks to the height of 6 metres; two-thirds of the metal were thus lost. Action of Water upon Basic Salts of Copper.G. Rousseau and G. Tite.-Water converts a great number of neutral metallic salts into basic salts by a The Determination of Nitric and Nitrous Acids in Spring Waters.-Max Rosenfeld.-This paper will be inserted in full. Determination of the Ignition Temperature of Explosives.-Ch. E. Monroe.-From the Jour. Amer. Chem. Soc. Apparatus for Determining Carbonic Acid in Carbonates.-M. Finkener.-This paper requires the accompanying figure. Determination of Dry Matter in Fibrous Material. process the laws of which have been discovered by M.-O. Knöfler (Papier Zeitung).-Already inserted. A Mode of the Present Formation of Mineral Sulphides.-E. Chuard.-The author, after referring to the observations of Daubrée (Comptes Rendus, vol. lxxx., p. 461), on the formation of mineral species in hot sulphur springs points out that mineral sulphides occur to such an extent in the superficial strata of the globe that we can. not ascribe their formation to this cause alone. Researches on Thallium.-C. Lepierre and Lachaud -The authors have studied the action of dilute potassa upon thallium chromate, that of concentrated potassa, that of melting potassa upon thallous chromate, that of melted potassium nitrate upon the same chromate, and jastly, they have examined thallium chloro chromate. On the Parabanic and Oxaluric Acids.-W. C. Matignon. The author investigates these acids from a thermo-chemical point of view. Transformation of Gallic Acid and of Tannic into Benzoic Acid.-Ch. Er. Guignet.-A mixture of ammonia and zinc powder is placed in a flask closed with a stopper, through which passes a tube drawn out to a point. Heat is applied, and when the evolution of hydrogen is quite regular a hot solution of gallic acid is gradually added. If the temperature is kept at 60°, the gallic acid is completely transformed in a few hours. It is changed first into salicylic and then into benzoic acid. Under the same conditions tannin (digallic acid) is also converted into benzoic acid. Acid Polymers of Ricinoleic Acid.-M. ScheurerKestner.-Polymerisation may be pushed as far as to the tetra- and pentaricinoleic acids. As the polymerisation advances, the acid properties of the new compounds decrease. On Panary Fermentation.-Léon Boutroux.-Panary fermentation consists essentially in the normal alcoholic fermentation of the sugar pre-existing in the flour. The leaven produces the disengagement of gases which raise the bread, and it hinders the development of the parasitic bacteria of the flour and the water from turning the paste sour and dissolving the gluten. Transformation of Oxycarbonated Hæmoglobine and Methæmoglobine, and on a New Method of Detecting Carbon Monoxide in Blood.-H. Bertin Small Laboratory Appliances: Filtration with Reduced Pressure.-J. F. Stoddart.-From the four. Anal. Chem. Treatment of Filter Paper with Nitric Acid at 142. This device is successful, as the paper is not only strengthened but filters better. A Vacuum Apparatus for Small Laboratories.E. Dietrich (Pharm. Central Halle).-The air is rarefied by means of a water-pump. Notes on Sodium Carbonate.-R. Kissling and L. Dobbin. For the substance of this note we must refer to the Zeit. fur Angew. Chemie. New Determinations of the Specific Gravity of Sulphuric Acid of Different Strengths.-G. Lunge and Isler.-A series of tables. On Lacmoid.-O. Foerster.-This paper will be inserted in full. The Behaviour of Acids with Litmus.-J. E Marsh. From the CHEMICAL NEWS. On Electrolysis.-Edgar F. Smith and Lee K. Frankel. From the Amer. Chem. Jour., the Jour. Anal. Chem., and the Four. Franklin Institute. A Volumetric Method for Determining Sulphuric Acid in Sulphates.-Launcelot W. Andrews. From the Amer. Chem. Jour. The Reduction of Barium Sulphate to Sulphide on Ignition with the Carbon of the Filter.-C. W. Marsh (Four. Anal. Chem.). Determination of Silica in Silicates by Fusion with Alkaline Silicates.-James P. Gilbert.-From the Tech. Quart., with reference to papers on the same subject by George Craig and David Lindo (CHEMICAL NEWS). A Modification of Elementary Analysis with Lead Chromate.-Rudolf de Roode.-From the Amer. Chem. Four. The Simultaneous Determination of Sulphur and Carbon.-L. Prunier.-From the Comptes Rendus. Determination of Sulphur in Organic Substances. -W. Burton.-From the Amer. Chem. Four. Determination of Acetone in Wood Spirit.-L. Vignon and G. Arachequesne.-From th Comptes Rendus. NEW EDITION. Sans and J. Moitessier.-These researches contradict the PIESSE'S ART OF PERFUMERY. conclusions of Th. Weil and B. von Anrep regarding the existence of a combination of methæmoglobine with carbon monoxide. The carbonic oxide contained in the solutions of methæmoglobine behaves exactly as if it was dissolved in water. Hence it is easy to detect minimum quantities of carbon monoxide in blood. Methods of Obtaining the Odours of Plants. Instructions for the Manufacture of Perfumes PRICE 10s. 6D. PIESSE & LUBIN, 2, NEW BOND STREET, LONDON. SCHOLARSHIPS AND PRIZES. - Two Entrance Science Scholarships, value £75 and £50, and two Buxton Scholarships, value Aug. 14, 1891. SALICYLATES. MANUFACTURED UNDER KOLBE'S PROCESS BY J. HAUFF, FEUERBACH-STUTTGART. FUERST BROS.,17, PHILPOT LANE, £30 and £20, will be offered for competition at the end of September FUERST to new Students-Sixteen other Scholarships and Prizes are given The Metropolitan, Metropolitan District, East London, and South MUNRO SCOTT, Warden. GAS DEPARTMENT. OXIDE OF IRON. LONDON, E.C Telegrams-"FUERST LONDON." Telephone No. 1050. N.B. Stock kept in London. To MANUFACTURERS OF ANILINES and ANILINE DERIVATIVES. SODIUM. THE ALUMINIUM COMPANY, LIMITED, are prepared to supply this hitherto expensive reagent in any The Gas Committee are prepared to receive quantity at very cheap rates. For full particulars address Tenders for the supply of 500 tons Oxide of Iron for purify ing the gas at their Works. Forms of tender and further particulars may be obtained on application to the Gas Engineer, Gas Offices, Bloom St., Salford. Sealed tenders endorsed Oxide," to be sent to me not later than 5 p m. on Thursday, the 20th inst. Town Hall, Salford, By Order, SAMUEL BROWN, Town Clerk. CHARCOAL. LUMP, FILTERING, POWDERED. &c. ACETATE OF LIME. WOOD TAR, WOOD NAPHTHA (Solvent and Miscible). LAMPBLACK, FOUNDER'S BLACKING, PLUMBAGO, &c. J.. THE ALUMINIUM COMPANY, LIMITED, S. MERRY AND Co., ASSAYERS AND ANALYTICAL CHEMISTS, LYDBROOK CHEMICAL CO., 143, CANNON STREET, E.C. Works, Manchester. NEWS In the spectroscope itself advances have been made by Lord Rayleigh by his discussion of the theory of the instrument, and by Professor Rowland in the construction of concave gratings. Lord Rayleigh has shown that there is not the necessary connection, sometimes supposed, between dispersion and resolving power, as besides the prism or grating other ADVANCEMENT OF SCIENCE. details of construction and of adjustment of a spectroscope CARDIFF, 1891. ADDRESS OF THE PRESIDENT, D.C.L. (Oxon.), LL.D. (Cantab., Edin., et Dubl.), Ph.D. (Lugd. Bat.), F.R.S., F.R.A.S., Hon. F.R.S.E., &c., Correspondant de l'Institut de France. It is now many years since this Association has done honour to the science of Astronomy in the selection of its President. Since Sir George Airy occupied the Chair in 1851, and the late Lord Wrottesley nine years later in 1860, other sciences have been represented by the distinguished men who have presided over your meetings. The very remarkable discoveries in our knowledge of the heavens which have taken place during this period of thirty years-one of amazing and ever-increasing activity in all branches of science-have not passed unnoticed in the addresses of your successive Presidents; still it seems to me fitting that I should speak to you to-night chiefly of those newer methods of astronomical research which have led to those discoveries, and which have become possible by the introduction since 1860 into the observatory of the spectroscope and the modern photographic plate. In 1866 I had the honour of bringing before this Association, at one of the evening lectures, an account of the first-fruits of the novel and unexpected advances in our knowledge of the celestial bodies which followed rapidly upon Kirchhoff's original work on the solar spectrum and the interpretation of its lines. Since that time a great harvest has been gathered in the same field by many reapers. Spectroscopic astronomy has become a distinct and acknowledged branch of the science, possessing a large literature of its own and observatories specially devoted to it. The more recent discovery of the gelatine dry plate has given a further great impetus to this modern side of astronomy, and has opened a pathway into the unknown of which even an enthusiast thirty years ago would scarcely have dared to dream. must be taken into account. The resolving power of the prismatic spectroscope is proportional to the length of path in the dispersive medium. For the heavy flint glass used in Lord Rayleigh's experiments the thickness necessary to resolve the sodium lines came out 1'02 c.m. If this be taken as a unit the resolving power of a prism of similar glass will be in the neighbourhood of the sodium lines equal to the number of c.m. of its thickness. In other parts of the spectrum the resolving power will vary inversely as the third power of the wave-length, so that it will be eight times as great in the violet as in the red. The resolving power of a spectroscope is therefore proportional to the total thickness of the dispersive material in use, irrespective of the number, the angles, or the setting of the separate prisms into which, for the sake of convenience, it may be distributed. The resolving power of a grating depends upon the total number of lines on its surface and the order of spectrum in use, about 1000 lines being necessary to resolve the sodium lines in the first spectrum. As it is often of importance in the record of observations to state the efficiency of the spectroscope with which they were made, Professor Schuster has proposed the use of a unit of purity as well as of resolving power, for the full resolving power of a spectroscope is realised in practice only when a sufficiently narrow slit is used. The unit of purity also is to stand for the separation of two lines differing by one-thousandth of their own wavelength; about the separation of the sodium pair at D. A further limitation may come in from the physiological fact that, as Lord Rayleigh has pointed out, the eye when its full aperture is used is not a perfect instrument. If we wish to realise the full resolving power of a spectroscope, therefore, the emergent beam must not be larger than about one-third of the opening of the pupil. Up to the present time the standard of reference for nearly all spectroscopic work continues to be Ångström's map of the solar spectrum, and his scale based upon his original determinations of absolute wave-length. It is well known, as was pointed out by Thalén in his work on the spectrum of iron in 1884, that Ångstrom's figures are slightly too small in consequence of an error existing in a The corrections for this standard metre used by him. have been introduced into the tables of the wave-lengths of terrestrial spectra collected and revised by a Committee of this Association from 1885 to 1887. Last year the Committee added a table of corrections to Rowland's scale. The inconvenience caused by a change of standard scale is, for a time at least, considerable; but there is little doubt that in the near future Rowland's photographic In no science, perhaps, does the sober statement of the results which have been achieved appeal so strongly to the imagination, and make so evident the almost boundless powers of the mind of man. By means of its light alone to analyse the chemical nature of a far distant body; to be able to reason about its present state in relation to the past and future; to measure within an English mile or less per second the otherwise invisible motion which it may have towards or from us; to do more, to make even that which is darkness to our eyes light, and from vibra-map of the solar spectrum, and his scale based on the tions which our organs of sight are powerless to perceive to evolve a revelation in which we see mirrored some of the stages through which the stars may pass in their slow evolutional progress-surely the record of such achievements, however poor the form of words in which they may be described, is worthy to be regarded as the scientific epic of the present century. I do not purpose to attempt a survey of the progress of spectroscopic astronomy from its birth at Heidelberg in 1859, but to point out what we do know at present, as distinguished from what we do not know, of a few only determinations of absolute wave-length by Pierce and Bell, or the Potsdam scale based on original determina. tions by Müller and Kempf, which differs very slightly from it, will come to be exclusively adopted. The great accuracy of Rowland's photographic map is due chiefly to the introduction by him of concave gratings, and of a method for their use, by which the problem of the determination of relative wave lengths is simplified to measures of coincidences of the lines in different spectra by a micrometer. The concave grating and its peculiar mounting, in which no lenses or telescope are needed, and in which all the spectra are in focus together, formed a new departure, which their luminosity is due are almost always much of great importance in the measurement of spectral lines. greater than would be produced by encounters of moleThe valuable method of photographic sensitisers for cules having motions of translation no greater than the different parts of the spectrum has enabled Professor average motions which characterise the temperature of Rowland to include in his map the whole visible solar the gases as a whole. The temperature of a vacuum tube spectrum, as well as the ultra-violet portion as far as it through which an electric discharge is taking place may can get through our atmosphere. Some recent photo- be low, as shown by a thermometer, quite apart from the graphs of the solar spectrum, which include A, by Mr. | consideration of the extreme smallness of the mass of George Higgs, are of great technical beauty. gas; but the vibrations of the luminous molecules must be violent in whatever way we suppose them to be set up by the discharge. If we take Schuster's view, that comparatively few molecules are carrying the discharge, and that it is to the fierce encounters of these alone that the luminosity is due, then if all the molecules had similar motions the temperature of the gas would be very high. So in flames where chemical changes are in progress, the vibratory motions of the molecules which are luminous may be, in connection with the energy set free in these changes, very different from those corresponding to the mean temperature of the flame. During the past year the results of three independent researches have appeared, in which the special object of the observers has been to distinguish the lines which are due to our atmosphere from those which are truly solarthe maps of M. Thollon, which, owing to his lamented death just before their final completion, have assumed the character of a memorial of him; maps by Dr. Becker; and sets of photographs of a high and a low sun by Mr. McClean. At the meeting of this Association in Bath, M. Janssen gave an account of his own researches on the terrestrial lines of the solar spectrum, which owe their origin to the oxygen of our atmosphere. He discovered the remarkable fact that while one class of bands varies as the density of the gas, other diffuse bands vary as the square of the density. These observations are in accordance with the work of Egoroff and of Olszewski, and of Liveing and Dewar on condensed oxygen. In some recent experiments Olszewski, with a layer of liquid oxygen 30 m.m. thick, saw, as well as four other bands, the band coincident with Fraunhofer's A-a remarkable instance of the persistence of absorption through a great range of temperature. The light which passed through the liquid oxygen had a light blue colour resembling that of the sky. Of not less interest are the experiments of Knut Ångström, which show that the carbonic acid and aqueous vapour of the atmosphere reveal their presence by dark bands in the invisible infra-red region, at the positions of bands of emission of these substances. It is now some thirty years since the spectroscope gave us for the first time certain knowledge of the nature of the heavenly bodies, and revealed the fundamental fact that terrestrial matter is not peculiar to the solar system, but is common to all the stars which are visible to us. In the case of a star such as Capella, which has a spectrum almost identical with that of the sun, we feel justified in concluding that the matter of which it is built up is similar, and that its temperature is also high, and not very different from the solar temperature. The task of analysing the stars and nebula becomes, however, one of very great difficulty when we have to do with spectra differing from the solar type. We are thrown back upon the laboratory for the information necessary to enable us to interpret the indications of the spectroscope as to the chemical nature, the density and pressure, and the temperature of the celestial masses. What the spectroscope immediately reveals to us are the waves which were set up in the ether filling all interstellar space, years or hundreds of years ago, by the motions of the molecules of the celestial substances. As a rule it is only when a body is gaseous and sufficiently hot that the motions within its molecules can produce bright lines and a corresponding absorption. The spectra of the heavenly bodies are, indeed, to a great extent absorption spectra, but we have usually to study them through the corresponding emission spectra of bodies brought into the gaseous form and rendered luminous by means of flames or of electric discharges. In both cases, unfortunately, as has been shown recently by Professors Liveing and Dewar, Wüllner, E. Wiedemann, and others, there appears to be no certain direct relation between the luminous radiation as shown in the spectroscope and the temperature of the flame, or of the gaseous contents of the vacuum tube-that is, in the usual sense of the term as applied to the mean motion of all the molecules. both cases the vibratory motions within the molecules to In Under the ordinary conditions of terrestrial experiments, therefore, the temperature or the mean vis viva of the molecules may have no direct relation to the total radiation, which, on the other hand, is the sum of the radiation due to each luminous molecule. These phenomena have recently been discussed by Ebert from the standpoint of the electro-magnetic theory of light: Very great caution is therefore called for when we attempt to reason by the aid of laboratory experiments to the temperature of the heavenly bodies from their radiation, especially on the reasonable assumption that in them the luminosity is not ordinarily associated with chemical changes or with electrical discharges, but is due to a simple glowing from the ultimate conversion into molecular motion of the gravitational energy of shrinkage. In a recent paper Stas maintains that electric spectra are to be regarded as distinct from flame spectra and from researches of his own; that the pairs of lines of the sodium spectrum other than D are produced only by disruptive electric discharges. As these pairs of lines are found reversed in the solar spectrum, he concludes that the sun's radiation is due mainly to electric discharges. But Wolf and Diacon, and later, Watts, observed the other pairs of lines of the sodium spectrum when the vapour was raised above the ordinary temperature of the Bunsen flame. Recently Liveing and Dewar saw easily, besides D, the citron and green pairs, and sometimes the blue pair and the orange pair, when hydrogen charged with sodium vapour was burning at different pressures in oxygen. In the case of sodium vapour, therefore, and presumably in all other vapours and gases, it is a matter of indifference whether the necessary vibratory motion of the molecules is produced by electric discharges or by flames. presence of lines in the solar spectrum which we can only produce electrically is an indication, however, as Stas points out, of the high temperature of the sun. The We must not forget that the light from the heavenly. bodies may consist of the combined radiations of different layers of gas at different temperatures, and possibly be further complicated to an unknown extent by the absorption of cooler portions of gas outside. Not less caution is needed if we endeavour to argue from the broadening of lines and the coming in of a continuous spectrum as to the relative pressure of the gas in the celestial atmospheres. On the one hand it cannot be gainsaid that in the laboratory the widening of the lines in a Plücker's tube follows upon increasing the density of the residue of hydrogen in the tube, when the vibrations are more frequently disturbed by fresh encounters, and that a broadening of the sodium lines in a flame at ordinary pressure is produced by an increase of the quantity of sodium in the flame; but it is doubtful if pressure, as distinguished from quantity, does produce an increase of the breadth of the lines. An individual mole. cule of sodium will be sensibly in the same condition, considering the relatively enormous number of the mole. cules of the other gases, whether the flame is scantily or copiously fed with the sodium salt. With a small quantity of sodium vapour the intensity will be feeble, except near the maximum of the lines; when, however, the quantity is increased, the comparative transparency on the sides of the maximum will allow the light from the additional molecules met with in the path of the visual ray to strengthen the radiation of the molecules farther back, and so increase the breadth of the lines. In a gaseous mixture it is found, as a rule, that at the same pressure or temperature, as the encounters with similar molecules become fewer, the spectral lines will be affected as if the body were observed under conditions of reduced quantity or temperature. In their recent investigation of the spectroscopic behaviour of flames under various pressures up to forty atmospheres, Professors Liveing and Dewar have come to the conclusion that though the prominent feature of the light emitted by flames at high pressure appears to be a strong continuous spectrum, there is not the slightest indication that this continuous spectrum is produced by the broadening of the lines of the same gases at low pressure. On the contrary, photometric observations of the brightness of the continuous spectrum, as the pressure is varied, show that it is mainly produced by the mutual action of the molecules of a gas. Experiments on the sodium spectrum were carried up to a pressure of forty atmospheres without producing any definite effect on the width of the lines which could be ascribed to the pressure. In a similar way the lines of the spectrum of water showed no signs of expansion up to twelve atmospheres; though more intense than at ordinary pressure, they remained narrow and clearly defined. It follows, therefore, that a continuous spectrum cannot be considered, when taken alone, as a sure indication of matter in the liquid or the solid state. Not only, as in the experiments already mentioned, such a spectrum may be due to gas when under pressure, but, as Maxwell pointed out, if the thickness of a medium, such as sodium vapour, which radiates and absorbs different kinds of light, be very great, and the temperature high, the light emitted will be of exactly the same composition as that emitted by lamp-black at the same temperature, for the radiations which are feebly emitted will be also feebly absorbed, and can reach the surface from immense depths. Schuster has shown that oxygen, even in a partially exhausted tube, can give a continuous spectrum when excited by a feeble electric discharge. Compound bodies are usually distinguished by a banded spectrum; but on the other hand such a spectrum does not necessarily show the presence of compounds, that is, of molecules containing different kinds of atoms, but simply of a more complex molecule, which may be made up of similar atoms, and be therefore an allotropic condition of the same body. In some cases, for example, in the diffuse bands of the absorption spectrum of oxygen, the bands may have an intensity proportional to the square of the density of the gas, and may be due either to the formation of more complex molecules of the gas with increase of pressure, or it may be to the constraint to which the molecules are subject during their encounters with one another. It may be thought that at least in the coincidences of bright lines we are on the solid ground of certainty, since the length of the waves set up in the ether by a molecule, say of hydrogen, is the most fixed and absolutely permanent quantity in nature, and is so of physical necessity, for with any alteration the molecule would cease to be hydrogen. Such would be the case if the coincidence were certain; but an absolute coincidence can be only a matter of greater or less probability, depending on the resolving power employed, on the number of the lines which correspond, and on their characters. When the coincidences are very numerous, as in the case of iron and the solar spectrum, or the lines are characteristically grouped, as in the case of hydrogen and the solar spectrum, we may regard the coincidence as certain; but the progress of science has been greatly retarded by resting important conclusions upon the apparent coincidence of single lines, in spectroscopes of very small resolving power. In such cases, unless other reasons supporting the coincidence are present, the probability of a real coincidence is almost too small to be of any importance, especially in the case of a heavenly body which may have a motion of approach or of recession of unknown amount. But even here we are met by the confusion introduced by multiple spectra, corresponding to different molecular groupings of the same substance; and, further, to the influence of substances in vapour upon each other; for when several gases are present together, the phenomena of radiation and reversal by absorption are by no means the same as if the gases were free from each other's influence, and especially is this the case when they are illuminated by an electric discharge. I have said as much as time will permit, and I think indeed sufficient, to show that it is only by the laborious and slow process of most cautious observation that the foundations of the science of celestial physics can be surely laid. We are at present in a time of transition when the earlier, and, in the nature of things, less precise observations are giving place to work of an order of accuracy much greater than was formerly considered attainable with objects of such small brightness as the stars. The accuracy of the earlier determinations of the spectra of the terrestrial elements are in most cases insufficient for modern work on the stars as well as on the sun. They fall much below the scale adopted in Rowland's map of the sun, as well as below the degree of accuracy attained at Potsdam by photography in a part of the spectrum for the brighter stars. Increase of resolving power very frequently breaks up into groups, in the spectra of the sun and stars, the lines which had been regarded as single, and their supposed coincidences with terrestrial lines fall to the ground. For this reason many of the early conclusions, based on observation as good as it was possible to make at the time with the less powerful spectroscopes then in use, may not be found to be maintained under the much greater resolving power of modern instruments. The spectroscope has failed as yet to interpret for us the remarkable spectrum of the Aurora Borealis. Undoubtedly in this phenomenon portions of our atmosphere are lighted up by electric discharges; we should expect, therefore, to recognise the spectra of the gases known to be present in it. As yet we have not been able to obtain similar spectra from these gases artificially, and especially we do not know the origin of the principal line in the green, which often appears alone, and may have therefore an origin independent of that of the other lines. Recently the suggestion has been made that the Aurora is a phenomenon produced by the dust of meteors and falling stars, and that near positions of certain auroral lines to lines or flutings of manganese, lead, barium, thallium, iron, &c., are sufficient to justify us in regarding meteoric dust in the atmosphere as the origin of the auroral spectrum. Liveing and Dewar have made a conclusive research on this point, by availing themselves of the dust of excessive minuteness thrown off from the surface of electrodes of various metals and meteorites by a disruptive discharge, and carried forward into the tube of observation by a more or less rapid current of air or other gas. These experiments prove that metallic dust, however fine, suspended in a gas will not act like gaseous matter in becoming luminous with its characteristic spectrum in an electric discharge, similar to that of the Aurora. Professor Schuster has suggested that the principal line may be due to some very light gas which is present in too small a proportion to be detected by chemical analysis, or even by the spectroscope in the |