Slike strani
PDF
ePub

one made by Sir William Herschel. In a paper communicated by him to the Royal Society in December, 1781, he reviews the serious difficulties involved in determining the parallax of a star by comparing its zenith distance at different times of the year. Especially there is the uncertainty introduced by the refraction of light, and in addition as the angular distances of stars from the zenith are changed by precession, nutation, and aberration, any errors in the calculated amount of these changes will all affect the results. He proposed, therefore, to examine with his big telescope the bright stars and see which of them had faint stars near them. The bright stars, he said, are probably much nearer than the faint stars; and if the parallax does not even amount to 1" the case is by no means desperate. With a large telescope of very great perfection it should be possible to detect changes in the angular distance of two neighbouring stars. By this differential method the difficulties inherent in the method of zenith distances will be eliminated. Herschel made a great survey to find suitable stars, and in this way was led to the discovery of double stars-i.e. of pairs of stars which are physically connected and revolve around one another, just like sun and earth. This was a most important discovery, but as the two components of a double star are practically at the same distance from us they do not serve to determine parallax, for which we need one star to serve as a distant mark.

For another forty years persistent efforts were made without success. Piazzi, in Italy, thought he had detected parallax in Sirius and a number of other bright stars, but the changes he detected in the zenith distances were unquestionably due to errors introduced by uncertainty in refraction, or slight changes in the position of his instruments in the course of the year. Dr. Brinkley, in Dublin, made a gallant effort and took the greatest pains. He thought he had succeeded, and for many years there was a controversy between him and Pond as to whether his results were trustworthy. The state of knowledge of the distances of the fixed stars in 1823 is summed up accurately by Pond in the Philosophical Transactions :

:

"The History of annual parallax appears to me to be this in proportion as instruments have been imperfect in their construction, they have misled observers into the belief of the existence of sensible parallax. This has happened in Italy to astronomers of the very first reputation. The Dublin instrument is superior to any of a similar construction on the Continent; and accordingly it shows a much less parallax than the Italian astronomers imagined they had detected. Conceiving that I have established, beyond a doubt, that the Greenwich instrument approaches still nearer to perfection, I can come to no other conclusion than that this is the reason why it discovers no parallax at all."

Besides these and other efforts to find parallax in the zenith distances of stars, attempts were also made to detect changes in the time at which the stars cross the meridian, to see if they are slightly before their time at one period of the year and slightly after it at another. But these, too, were unsuccessful, even in the hands of astronomers like Bessel and Struve. The best were some observations of circumpolar stars made by Struve in Dorpat between 1814 and 1821. The following table shows some of the results at which he arrived :

[merged small][merged small][merged small][merged small][ocr errors][merged small]

+1.099 +0.175±0.127 +0·402 +0.305±0.071 +1.147 +0.134±0.139 +1.138 +0.020 ±0.117

This table has the merit of not looking wildly impossible in the present state of our knowledge. It has the disadvantage of not giving a definite parallax to each star. For example, it is impossible to say how much of the 0.134" is to be given to Capella and how much to ẞ Draconis. Further, the probable errors, though really small, are nearly as large as the quantities determined.

Struve and Bessel therefore attempted the problem by the differential method recommended by Herschel. By this time it had become easier to carry out. The method of mounting telescopes equatorially had been devised, so that the telescope was always kept pointing to the same part of the sky by clockwork-driven mechanism. Struve chose the bright star a Lyræ, and measured its distance from a faint star about 40" away on ninety-six nights between November, 1835, and August, 1838. In the focal plane of his telescope he had what is called a position micrometer. micrometer contains two parallel spider-threads. stretched on frames, and the frames are movable by screws until the position shown in the diagram is reached the distance apart of the threads is known by the readings of the screw-heads. He found that a Lyræ had a parallax 0-262" with a probable error ±0.025".

The

Bessel chose the star 61 Cygni as a likely star to be near the sun, and therefore to have appreciable parallax. 61 Cygni is not nearly so bright as a Lyræ, but has a very great angular movement or propermotion among the stars. Bessel used an instrument called a heliometer. Like Struve's telescope, it was mounted so that it could be driven by clockwork to point always at the same star. The object-glass of Bessel's telescope was made by the great optician Fraunhofer, with the intention of cutting it in halves. Fraunhofer died before the time came to carry out this delicate operation, but it was successfully accomplished after his death.

Delicate mechanism was provided for turning the glass, and also for moving the two halves, the amount of movement being very accurately measured by screws. Each half gives a perfect image of any object which is examined, but the two images are shifted by an amount equal to the distance one-half of the lens is moved along the other. Thus when a bright star and faint star are looked at, one-half of the object-glass can be made to give images S and s, and the other half S' and s'. By moving the screw exactly the right amount s' can be made to coincide with S, and the reading of the screw gives a measure of the angular distance between the two stars. Bessel made observations on ninetyeight nights extending from August, 1837, to September, 1838. The table, taken from a report by Main (Mem. R.A.S., vol. xii., p. 29), shows how closely the mean of the observations for each month accords with the supposition that the star has the parallax 0.369" :

[merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]

Simultaneously with these determinations of the distance of a Lyræ and 61 Cygni, the distance of a Centauri, one of the brightest of the southern stars, was found by Henderson from observations of zenith distance made by him at the Cape between April, 1832, and May, 1833. He learnt just before the termination of his residence at the Cape that this star had a very large proper-motion. Suspecting a possible parallax, he examined the observations when he had taken up his new office of Astronomer Royal for Scotland, and found a parallax amounting to 0.92". He did not, however, publish his results until he found that they were confirmed by the right ascensions. In a communication to the Royal Astronomical Society in December, 1838, he states that it is probable that the star has a parallax of 10".

The great and difficult problem which had occupied astronomers for many generations was thus solved for three separate stars in 1838

[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors]

(The unit of distance is that from the earth to the sun,) Henderson's

observation is interesting because a Centauri is, as far as we yet know, the nearest of all the stars to us. But by far the most valuable of these observations is Bessel's. The heliometer, which he devised, proved itself to be by far the most serviceable instrument for determining stellar parallax until the application of photography for this purpose.

The somewhat dramatic manner in which the distances of three stars were determined in the same year, after several centuries of failures, may have led to the hope that the range of many more stars would soon be found. This was not the case, however. Each star had to be measured separately, and involved many nights of observations. The quantities to be measured were so small that they taxed the resources of the best instruments and best observers. In 1843 Peters published the parallaxes of half a dozen stars determined with the vertical circle at Pulkova, but the parallax of only one of these, Polaris, is obtained with much accuracy. With Bessel's heliometer, Schlüter and Wichmann measured the distance of Gr. 1830, the star which had the largest known proper-motion. In the 'sixties, Auwers with the same instrument determined the parallax of several quickmoving stars, and also of the bright start Procyon. With the Bonn heliometer, Krueger in the 'sixties | measured the distance of three stars, and Winnecke two more. Other observations were made, amongst others, by Maclear, Otto Struve, Brünnow, and Ball; but as these observers had not such suitable instru

ments, their results were not of the same high standard of value. A generous estimate would place the number of stars the distances of which had been satisfactorily determined before 1880 at not more than twenty.

In the 'eighties, progress became more rapid. Gill, the Astronomer Royal for the Cape, in conjunction with a young American astronomer, Elkin, determined with great accuracy, though with only a small 4-in. heliometer, the distance of nine stars of the southern hemisphere. These stars included a Centauri, and the bright stars Sirius and Canopus. These results were communicated to the Royal Astronomical Society in 1884. The work of Gill and Elkin did not stop there. After some years, a very fine 7-in. heliometer was obtained at the Cape, and with it, between 1888 and 1898, the parallaxes of seventeen stars were deter

mined by Gill and his assistants with very great accuracy. The stars observed at the Cape consisted of the brightest stars of the southern hemisphere, and of the stars with the greatest proper-motions. The results were remarkable. The stars with large proper-motions were nearly always comparatively near -say within one million times the sun's distance. On the other hand, some of the very brightest stars, particularly Canopus, the brightest star in the sky after Sirius, were at vastly greater distances.

Meanwhile, Elkin, who had been appointed director of the Yale Observatory in 1884, carried out with a 6-in. heliometer, between the years 1885 and 1892, a determination of the distances of the ten brightest stars of the northern hemisphere. After these were finished the Yale observers, Elkin, Chase, and Smith, embarked on the ambitious programme of the determination of the distances of 163 stars of the northern hemisphere which show large proper-motion. They have added forty-one southern stars to these, and thirty-five stars of special interest. The results of all these observations were published in 1912. They have not, in most cases, the high accuracy of the Cape observations, but, nevertheless, are of great accuracy, and appear to be free from any considerable systematic error. A third important series of observations was made by Peter with a 6-in. heliometer at Leipzig. These were commenced about 1890, and continued until the death of Prof. Peter in 1911. The parallaxes of twenty stars were determined with the same high accuracy as the Cape observations. Observations with the heliometer require both skill and industry. To secure the needful accuracy measures must be made in four different positions of the instrument, SO that possible small systematic errors may be eliminated by reversal. Great care is required in the adjustments of the instrument, particularly in the accurate determination of the scale-value at different temperatures. The possibility of obtaining satisfactory results with less labour was considered by Kapteyn, in view of the successful determination of the parallax of Gr. 34 by Auwers. From 1885 to 1887 he made observations with the transit-circle at Leyden of fifteen stars for the purposes of determining parallax. The observation consisted in observing the time when the star the parallax of which was sought and two or three neighbouring stars crossed the meridian. Observations are made at the two most favourable epochs -say every night in March, and every night in September-to determine whether the star has changed its position relatively to its neighbours in the interval. The difficulties are twofold. The purely accidental error of observations of transits is considerable as compared with the small quantity which is sought. Besides this, the star of which the parallax is required is probably brighter than the comparison stars, and special precautions are required to guard against personal errors of the observer.

In questions of this kind the only satisfactory way is to judge by the results. From observations made on fifty nights, values of the parallax are obtained not nearly so accurate as the best heliometer observations, but still of considerable accuracy. Finally, the parallaxes of four of the stars which had been previously determined by measures with a heliometer showed satisfactory agreement.

This method has been employed by Jöst at Heidelberg, very extensively by Flint at the Washburn Observatory of the University of Wisconsin, and is now being tried at the Cape by Vouté, a pupil of Kapteyn's. It appears to me that this method can never give results of the highest accuracy, but that it may be of use in a preliminary search for stars of large parallax. The argument of the facility of the method

compared with the heliometer has, however, lost much of its force; for, as I hope to show next, the highest accuracy attainable with the heliometer can be secured much more easily with a photographic telescope.

The application of photography to the determination of stellar parallax was first made by Pritchard in Oxford between 1887 and 1889. He took a large number of photographs and measured on them the angular distance of the star which he was considering from four of its neighbours. In this way he determined the parallax of five stars. He began this work late in life, and it was left for others to develop the photographic method and find what accuracy could be attained with it. At first sight it seems very easy, but experience shows that there are a number of small errors which can creep in and vitiate the results, unless care is taken to avoid them.

It has gradually become clear that with a few simple precautions and contrivances, a greater accuracy can be reached in the determination of parallax by photography and with much less trouble than by any other method. Between 1895 and 1905, several astronomers succeeded in obtaining from a few plates results as accurate as could be obtained from many nights' observations with the heliometer by the most skilled observers. In the last five years a large number of determinations have been made. In 1910 Schlesinger published the parallaxes of twenty-five stars from photographs taken with the 40-in. refractor of the Yerkes Observatory, and in 1911 Russell published the parallaxes of forty stars from photographs taken by Hinks and himself at Cambridge. The opinion expressed by Gill on these observations (M.N., vol. lxii., p. 325), was that but for the wonderful precision of the Yerkes observations, the Cambridge results would have been regarded as of the highest class. The facility with which the Yerkes results are obtainable is expressed very tersely by Schlesinger"the number of stellar parallaxes that can be determined per annum, will in the long run be about equal to the number of clear nights available for the work." With the heliometer at least ten times as much time would have been required. During the last year two further instalments of the results of the Yerkes Observatory have been published by Slocum and Mitchell, giving the parallaxes of more than fifty stars. It might be thought that the high accuracy attained by them is largely attributable to the great length of the telescope. From experience at Greenwich, I do not think this is the case, and believe that similar results are obtainable with telescopes of shorter focal length. As several observatories are now occupied with this work, we may expect that the number of stars the distances of which are fairly well known will soon amount to thousands, as compared with three in 1838, about twenty in 1880, about sixty in 1900, and now perhaps two hundred.

The stars the distances of which have been measured have generally been specially selected on account of their brightness or large proper-motion. Lach star has been examined individually. Kapteyn has suggested that instead of examining stars singly in this way, photography gives an opportunity of examining all the stars in a small area of the sky simultaneously, and picking out the near ones. The method has been tried by Kapteyn and others-among them Dr. Rambaut. The idea is very attractive, because it examines the average star and not the bright star or star of larger proper-motion. It is liable, however, to some errors of systematic character, especially as regards stars of different magnitudes. Comparison of the results so obtained with those found otherwise will demonstrate whether these errors can be kept sufficiently small by great care in taking the photographs. Until this is done no opinion can be expressed on

the success of this experiment, which is worth careful trial.

The question may be asked, How near must a star be to us for its distance to be measurable? I think we may say ten million times the sun's distance. This corresponds to the small angle 0-02" for the parallax. If a star's parallax amounts to this, there are, I believe, several observatories where it could be detected with reasonable security, though we shall know more certainly by the comparison of the results of different observations when they accumulate.

You will readily imagine that an accurate knowledge of the distances of many stars will be of great service to astronomy. There are ample data to determine the positions, velocities, luminosities, and masses of many stars if only the distances can be found. Thus we know the distance of Sirius, and we are able to say that it is travelling in a certain direction with a velocity of so many miles per second: that it gives out forty-eight times as much light as the sun, but is only two and a half times as massive. The collection and classification of particulars of this kind is certain to give many interesting and perhaps surprising results. But it is not my purpose to deal with this to-night. The task I set before myself in this lecture was to give an idea of the difficulties which astronomers have gradually surmounted, and the extent to which they have succeeded in measuring the distances of the stars.

UNIVERSITY AND EDUCATIONAL
INTELLIGENCE.

Cambridge.—The Rev. T. C. Fitzpatrick, president of Queens' College, has been elected Vice-Chancellor for the coming academic year.

The council of the Senate has announced that the Board of Education has agreed to make a grant in aid of the medical departments of the University, and that the amount to be received on account of the present year is 58731.; it proposes that a new committee, to be called the Medical Grant Committee, should be appointed for the purpose of administering the annual grant.

Mr. H. Scott, of Trinity College, has been appointed curator in entomology for five years from March last. A grant of 50l. has been made from the Balfour Fund to enable Mr. G. Matthai, of Emmanuel College, to visit America in furtherance of his researches on the comparative anatomy and classification of the Madreporaria.

GLASGOW. By an Order in Council dated May 27, 1915, the King has reappointed Sir Donald MacAlister and Mr. Otto Beit, and has appointed Mr. R. E. Prothero, to be members of the governing body of the Imperial College of Science and Technology for a term of four years from June 1, 1915.

LONDON.-Owing to Prof. Brodie's services being required for military purposes, the course of advanced lectures in physiology arranged to be given by him at King's College (as announced last week) will not

be delivered.

OXFORD. The report of the delegates of the University Museum for 1914, together with the departmental reports of the professors and readers teaching within the Museum, has just been published. In the general report attention is directed to the departure of large numbers of the teaching and service staff, and also of research workers, for military duties. This has affected both the Museum itself and also the several departments. Mention is made of the billeting of the 9th Battalion of the Hampshire Regiment for a night in some of the laboratories; of the presentation to the University of Mr. Hope Pinker's

statue of Roger Bacon; and cf the completion of the carving in the upper corridor, under the bequest of the late Rev. H. T. Morgan.

The report of the Professor of Pathology records the fact that from an early date in August the department and the whole of its staff were engaged in services connected with the war. About 6000 inoculations were performed, and a quantity of vaccine was sent to Belgium. The Professor of Physiology includes in his report a tribute to the services rendered by the late Dr. G. J. Burch, F.R.S., and an account of the arrangements for the memorial to the late Prof. Francis Gotch, F.R.S. Most of the departmental reports, including that of the Curator of the Pitt-Rivers Museum, contain long lists of donations to the respective collections, and full records of the research work which, in spite of all obstacles, has been carried on in the various laboratories and workrooms of the Museum.

was

The new building for engineering science finished at Christmas. The new chemical laboratory is still in course of erection, but the professor hopes that it will be ready for occupation by next October.

Science announces that the Michigan Legislature has granted 70,000l. for the erection of a new university library building for the University of Michigan.

THE fiftieth anniversary celebration of the Worcester Polytechnic Institute, Worcester, Massachusetts, is to be held on June 6-10. President Wilson, who gave the opening address on a similar occasion twenty-five years ago, hopes, if the pressure of public business makes it possible, to attend the meetings on June 9. General G. W. Goethals has also accepted an invitation to be present. On June 10, honours are to be conferred and various bronze tablets unveiled.

A FREE Scholarship of the value of 30l., open to allcomers, and tenable at the Northampton Polytechnic Institute (London), is being offered to students. In view of the opportunities for advancement which the calling and craft of optics now offer on account of the shutting off cf alien supplies due to the war, the "Aitchison Memorial Scholarship," which has for its special object the encouragement of recruits for the optical industry, should prove very attractive to intelligent youths. The subjects of examination include English, mathematics, and elementary physics. The conditions of the scholarship have been laid down by a committee which includes Dr. R. Mullineux Walmsley, Prof. Silvanus P. Thompson, and Dr. J. W. Ettles. Full particulars can be had of the hon. secretary and treasurer, Mr. Henry F. Purser, 35 Charles Street, Hatton Garden, London, E.C.

SOCIETIES AND ACADEMIES.

LONDON.

Royal Society, May 20.-Sir William Crookes, president, in the chair.-H. Moore: The corpuscular radiation liberated in vapours by homogeneous X-radiation. -H. Richardson: The absorption in lead of y rays emitted by radium B and radium C. (1) The absorption curves in lead of the radiations emitted by

radium B and radium C have been determined and analysed. (2) In addition to the penetrating type of radiation for which u=0.5 (cm.-1) in lead, radium C has been found to emit soft types for which μ=46, μ=60, and μ=1.5, and which are practically absorbed by 1.5 cm. of lead. (3) The analysis of the radium B absorption curve shows that in addition to the radiation 40 in aluminium, the rays emitted consist of three types for which μ=46, μ=6·0, and μ=1.5 for lead. The close similarity of this latter radiation with

that of the soft portion emitted by radium C, already observed by Rutherford and Andrade, has been established. (4) The absorption of the radiations in different elements has been examined and the bearing of the results discussed. No evidence of anomalous absorption has been found in the case of the penetrating radiations.-T. R. Merton: The application of interference methods to the study of the origin of certain spectrum lines. By measuring the limiting orders at which interference can be detected for different radiations, certain deductions may be made as to the mass of the luminous particles and the temperature of the source. If the only circumstance which could possibly influence the width of spectrum lines at low pressures were the Doppler effect due to the motion of the luminous particles in the line of sight, the relative masses of particles emitting radiations from the same source of light might be calculated. As, however, there is reason to doubt the validity of this assumption under certain conditions, the conclusions which may be drawn with certainty from measurements of this kind are an inferior limit for the mass of the luminous particles if the temperature of the source is known, or a superior limit to the temperature if the mass of the luminous particles is assumed. It is shown in the paper that the flame lines of calcium, strontium, and barium are probably due to molecules, whilst the H and K lines of calcium are to be attributed to calcium atoms. As the flame lines are members of series, it must be recognised that radiations from molecules may give rise to line series as well as band spectra. Lines of the two spectra of argon have been investigated. The width of the lines of the red spectrum would appear to be accounted for by the Doppler effect. The lines of the blue spectrum are very broad in comparison with those of the red spectrum, and a satisfactory explanation of this has not been found. Spectrum lines of the "arc" type are broadened when condensed discharges are used as the method of excitation, but the difference in width of the lines in the blue and red spectra of argon is of another order of magnitude. The band spectrum associated with helium has been found to be enhanced when the gas is cooled to the temperature of liquid air, which might justify the suspicion that more than one atom was concerned in its production, but a comparison of the widths of the lines in the band spectrum with the ordinary helium lines makes it extremely probable that the band spectrum is due to atomic helium.

Physical Society, May 14.--Dr. A. Russell, vicepresident, in the chair.-E. H. Rayner: Precision resistance measurements with simple apparatus. The paper describes methods by which the comparison of resistances can be made to an accuracy of 1 in 10,000 or higher by using simple apparatus usually available in electrical laboratories, or which can be easily constructed with little skilled assistance. The comparison of nominally equal resistances of 1 ohm and upwards by the usual method of shunting one side of a nearly balanced quadrilateral by a high resistance is mentioned, and variations on this when only part of one resistance is shunted are often useful. The great advantages of having resistances capable of carrying comparatively large currents are illustrated, especially for measuring changes of resistance of commercial apparatus under working conditions. The determination of errors in a volt box for use with a potentiometer is described at some length. This is of especial importance in precision photometry. If a sufficient continuous-current voltage is not available for testing such apparatus as high-potential dividers, it is shown that using sufficient continuous current to secure sensitivity the heating may be supplied by superposed alternating current. Resistances in common use are

very generally of simple numerical value, and a Kelvin bridge specially designed for the comparison of such resistances is described. It consists essentially of two rows of 25 resistances of 20 ohms each.-G. F. W. Jordan: Some novel laboratory experiments. (1) Condensation calorimeters for the measurement of latent and specific heats. (a) It is shown how an ordinary vacuum jacket flask can be converted into a suitable condensation calorimeter. Errors arising from loss of heat and wetness of the vapour are almost eliminated by making two experiments. (b) Another condensation calorimeter is constructed on a different plan with a view to the elimination of the same errors. (2) The thermal conductivity of a narrow metal bar. Gray's apparatus for the measurement of the conductivity of a narrow bar has been modified for the purpose of rendering the loss of heat relatively small and reducing the time taken in the measurement, thus introducing the experiment to the elementary student. (3) The measurement of Poisson's ratio for a rectangular lath. Two mirrors are attached to opposite sides of the bent lath for the measurement of the anti-elastic radius of curvature, and Poisson's ratio is then deduced from the observations in the usual manner. (4) A method of measuring the coincidence period of a kater and a clock pendulum. The kater and the clock pendulums are electrically connected so that when at the centres of their swings a momentary current passes through a telephone receiver. (5) A differential telephone receiver. An ordinary receiver is connected to the secondary of a simple differentially wound transformer, and it is thus converted into a differential receiver for the purpose of electrical measurement. (6) Experiment on interference fringes. The fringes produced by a Lloyd's mirror in white light are nearly achromatised by a simple grating on smoked glass. Other suggestive interference effects with the grating are also described. -S. Butterworth: Electrically maintained vibrations.

The

Royal Meteorological Society, May 19.-Major H. G. Lyons, president, in the chair.-Dr. H. R. Mill and H. E. Carter: The wet winter of 1914-15. authors dealt fully with the abnormal rainfall of the four months, November, 1914, to February, 1915, and showed that the general rainfall for England and Wales for this period was 20-21 in. A striking feature of the comparison with the average is that the area with less than 12 in. of rain was barely one-tenth part of the area on the average map, while the area with more than 30 in. was nearly seven times as great as on the average map. December was by far the wettest month, the general rainfall being 211 per cent. of the average; in November it was 134 per cent.; in January 143 per cent.; and in February 198 per cent. of the average. The persistent nature of the rainfall caused extensive floods over practically all the lowlying parts of the country. The wettest previous winters were those of 1876-77 and 1911-12, that of 1914-15 was shown to be wetter than either of them. -J. E. Clark: Report on the phenological observations from December, 1913, to November, 1914. The report was based on the returns from 133 stations in various parts of the British Isles. This was the fourth successive mild year, the mean date for the plant records being a week earlier than the average. The dominating factors were the abnormally mild autumn of 1913, the mild winter, and remarkably genial April weather. Fruits and crops were prejudiced by the serious May frosts and droughty conditions from mid-April to October; on the other hand, the sunny warmth of the autumn largely contributed to make the year successful for the farmer and partially so to fruit-growers.

[ocr errors][merged small]

Academy of Sciences, May 25.-M. Ed. Perrier in the chair.-S. Lattès: Linear multiplicities invariant by a given linear substitution.-Ed. Bourquelot, M. Bridel, and A. Aubry: The biochemical synthesis of the a-mono-d-galactoside of ethylene glycol. The galactoside was obtained by the action of an extract of low yeast upon an aqueous solution of ethylene glycol and galactose during a period of nine months. A description is given of the process of purification, which offered some difficulties, and of the physical properties and hydrolysis of the a-galactoside.-Alphonse Berget : The capillary constant of sea water. From measurements of the surface tension of sea water and of distilled water it is shown that the difference is sufficiently great to cause an error in density measurements made with a hydrometer of rather more than one part in a thousand.-Pierre Lesage: The pedicels of Lunularia vulgaris.—Eugène Pittard: Comparative anthropometry of the Balkan peoples. Supplementing an earlier paper with statistics of the cephalic index and anthropometric characters of the face.-Jules Glover Telephony without transmission of the sound waves through air.-Jean Villey: A method for the radioscopic localisation of projectiles in the human body. The series of operations required by the one method are purely mechanical and dispense with calculations or photographic plates. Full details of the technique are given.-J. P. Dubarry: Anti-typhoid vaccination by the gastro-intestinal method. A comparison of the results obtained by the hypodermic and gastro-intestinal methods of inoculation.-E. Roubaud : The destruction of flies and the disinfection of bodies in the war zone. The use of cresylic acid, heavy tar oil, and ferric sulphate are recommended, and the specific action of each of these described.

CAPE TOWN.

66

L.

Royal Society of South Africa, April 21.-Dr. Péringuey, president, in the chair.-Dr. L. Péringuey Presidental Address :-"The Bushman as a Palæolithic Man."-Ethel M. Doidge: Some notes on the South African Erysiphacea. The paper consists of notes on the South African representatives of the powdery mildews." These cause a number of widely distributed and more or less destructive diseases of plants in this country; but they are not easily identified owing to the almost invariable absence of perithecia. The species occurring in South Africa are enumerated, and a list given of the specimens contained in the Union Mycological Herbarium, Pretoria. Two new specimens of the genus Uncinula are described.-A. W. Rogers: Geitsi Gubib, an old volcano: A geological description is given of Geitsi Gubib, a ring-shaped mountain in German South-West Africa, rising about 5200 ft. above sea-level, and a conspicuous object from the railway north of Keetmanshoop. The description is based on notes taken during a stay by the author of two days on the mountain, and on the examination of the rocks brought away.

[blocks in formation]
« PrejšnjaNaprej »