Popular Science Monthly/Volume 41/June 1892/Sketch of William Huggins
|SKETCH OF WILLIAM HUGGINS.|
DOCTOR HUGGINS is one of the leaders in the modern methods of astronomical research, and his name is associated with a considerable proportion of the discoveries that have been made respecting the constitution of the sun, stars, and nebulae, and with the results in general of the application of physical investigations and of spectroscopic observation in particular to the heavenly bodies.
William Huggins was born in London, February 7, 1824. He received his early education in the City of London School, and continued his studies in mathematics, the classics, and modern languages under private tutors. He devoted much time to experiments in natural philosophy, and by the aid of the apparatus which he collected he gained practical knowledge of the elements of the chief branches of physical science, including chemistry, electricity, and magnetism. He also studied, using the microscope, animal and vegetable physiology, and became in 1852 a member of the Microscopic Society. He developed a particular interest in astronomy, and, "under great difficulties," says one of the earlier biographies in Men of the Time, while still residing in the metropolis with his parents, "observed the planets and some of the double stars between the chimneys of London." The erection of an observatory in 1855, at his residence at Upper Tulse Hill, which he supplied with good instruments, gave him better opportunities for observation; and in 1858 he had an Alvan Clark telescope of eight inches aperture, mounted equatorially. He occupied himself here for some time with observation of double stars, and with careful drawings of the planets Mars, Jupiter, and Saturn. In the light of the knowledge gained in his physical studies he was not satisfied to follow in the beaten track of observation, but sought to broaden the field of study, and inquire as far as possible into the physical qualities of the sun and stars. A means of conducting investigations of this kind, which his predecessors had not possessed, was offered in the method of spectrum analysis discovered by Kirchhoff; and he was first able to undertake the application of this method in the beginning of 1862. In preparation for the research he mapped the spectra of twenty-six of the chemical elements, publishing the results of his labors in the Philosophical Transactions of the Royal Society. In conjunction with Dr. William Allen Miller, he compared the spectra of some fifty stars with those of several terrestrial elements, and found that the stars are hot bodies, similarly constituted with our sun, and containing many of the substances found on the earth. In 1864 he and Prof. Miller reported to the Royal Society the results of their observations of the spectra of the planets Venus, Mars, Jupiter, and Saturn; but they had found the light from Uranus too faint to be satisfactorily examined with the spectroscope.
The study of Uranus was resumed with an improved telescope in 1871 by Mr. Huggins, and he found its spectrum to be continuous so far as the feebleness of its light permitted it to be traced, or from C to near G. A photograph of the spectrum of Sirius was obtained by Mr. Huggins and Prof. Miller in 1863, when observations were suspended. They were resumed by Mr. Huggins in 1876, with apparatus so arranged that the spectrum of the sun could be taken on the same plate, and this method was applied to other bright stars. After recording in his communication to the Royal Society his expectation, with apparatus then under construction, of obtaining finer lines which might be present in the stellar light than those that had been seen, and of extending the photographic method to stars that were less bright, Prof. Huggins referred in general terms to "the many important questions in connection with which photographic observations of stars may be of value." Another paper recording the progress of these investigations to the end of 1879 named thirteen bright stars, Venus, Mars, and Jupiter, and different small areas of the moon, to which the method had been applied. Six of the spectra belonged to stars of the white class, while Arcturus seemed to present a spectrum "on the other side of that of the sun in the order of changes from the white-star group." The photographs of the planets showed no sensible planetary modification of the violet and ultra-violet parts of the spectrum. The results of the photographs of lunar areas taken under different conditions of illumination were negative as to any absorptive action of a lunar atmosphere. The author was then preparing to attempt to obtain by photography any lines which might exist in the violet and ultra-violet spectra of the gaseous nebulae. He further pointed out "the suitability of the photographic method of stellar spectrospcopy, first inaugurated by his researches, to some other investigations, such as differences which may present themselves in the photographic region in the case of the variable stars, the difference of relative motion of two stars in the line of sight, the sun's rotation from photographic spectra of opposite limbs, and the spectra of the different parts of a sun-spot." The British Association address of 1891 includes a fine summary of the results to date of observations of this character as they bear upon the evolutional order in which in this paper he arranged the stars from their photographic spectra. Substantially the same order had been proposed by Vogel in his classification of the stars in 1874.
Dr. Huggins presented a paper on his examination of the great nebula in Orion in 1868, and referred in it to earlier observations. The discussion was continued in 1872, and in 1882, when the author threw out the suggestion of a hope that the further knowledge of the spectra of the nebulae afforded us by photography might lead, by the help of terrestrial experiments, to more definite knowledge as to the state of things existing in those bodies. In communications to the French Academy of Sciences and to the Royal Society in 1889 he considered it probable that nebulae yielding a spectrum of luminous rays, with a very faint continuous spectrum, which is probably formed in part by luminous rays in close proximity, are at or near the beginning of the cycle of their celestial evolution. "They consist probably of gas at a high temperature and very tenuous, where chemical dissociation exists, and the constituents of the mass, doubtless, are arranged in the order of vapor density. As to the conditions which may have been anterior to this state of things the spectroscope is silent. We are free, so far as the spectroscope can inform us, to adopt the hypothesis which other considerations make most probable. On Dr. Croll's form of the impact theory of stellar evolution, which begins by assuming the existence of stellar masses in motion, and considers all subsequent evolutional stages to be due to the energy of this motion converted into heat by the collision of two such bodies, these nebulae would represent the second stage in which these existing solid bodies had been converted into a gas of very high temperature. They would take the same place, if we assume, with Sir William Thomson, the coming together of two or more cool, solid masses by the velocity due to their mutual gravitation alone. I pointed out in 1864 that the gaseous nature of these bodies would afford an explanation of the appearance of flat disks without condensation which many of them present. . . . In other gaseous nebulæ strong condensations are seen, and a stronger 'continuous' spectrum. The stage of evolution which the nebula in Andromeda represents is no longer a matter of hypothesis. The splendid photograph recently taken by Mr. Roberts of this nebula shows a planetary system at a somewhat advanced stage of evolution; already several planets have been thrown off, and the central gaseous mass has condensed to a moderate size as compared with the dimensions it must have possessed before any planets had been formed." In 1891, after more definitely describing the appearance of Mr. Roberts's photograph, he said that "to liken this object more directly to any particular stage in the formation of the solar system would be f to compare great things with small,' and might be indeed to introduce a false analogy; but, on the other hand, we should err through an excess of caution if we did not accept the remarkable features brought to light by this photograph as a presumptive indication of a progress of events in cosmical history following broadly upon the lines of Laplace's theory."
Dr. Huggins's spectrum observations on comets, in connection with those of other observers, satisfied him of the existence of different types, and that the same comet might present on one occasion one spectrum and on another the other spectrum; that they shine partly by reflected solar light and partly by their own light, the spectrum of which indicates the presence in the comet of carbon, possibly in combination with hydrogen. In the case of the Wells comet of 1882, he remarked that as Prof. A. Herschel and Dr. Von Konkoly had showed long before that the spectra of the periodic meteors are different for different swarms, it was not surprising that we now had a comet the matter of the nucleus of which under the sun's heat showed an essential chemical difference from the long series of hydrocarbon comets which had appeared since 1864. The spectrum of Coggia's comet (1874) indicated an approach to the earth of forty-six miles per second, while the real velocity of approach was only twenty-four miles per second. It was uncertain whether the whole or part of the difference in the velocity was due to the motion of the matter within the comet. It seemed probable, therefore, that the nucleus was solid, heated by the sun, and throwing out matter which formed the coma and tail; and part of this was in a gaseous form, giving the spectra of bright lines. The other portion existed probably in small incandescent particles; the polariscope showing that certainly not more than one fifth of the whole light was reflected solar light. In a paper on Photographing the Solar Corona without an Eclipse, Prof. Huggins spoke, in 1882, of problems of the highest interest in the physics of our sun connected with the varying forms of the coronal light which seemed to admit of solution only on the condition of its being possible to study the corona continuously, and to confront its changes with other visible phenomena presented by the sun. The spectroscopic method of viewing the prominences failed; experiments in looking at the corona through, screens of colored glass or other absorptive media had not been satisfactory. The author had therefore undertaken to use photography, and had satisfied himself that under certain conditions of exposure and development, a photographic plate could be made to record minute differences of illumination existing in different parts of a bright object, which was so subtle as to be at the very limit of the power of recognition of a trained eye, and even, perhaps, of those that surpassed that limit. Describing his apparatus and method, he showed that it was possible, by isolating through properly chosen absorbing media, the light of the sun in the violet part of the spectrum, to obtain photographs of the sun surrounded by an appearance distinctly coronal in its nature. He afterward found that, by using plates sensitive to violet light only, it was possible to do away with absorbing media and remove the difficulties that occurred in sifting the light. In 1886 Dr. Huggins accounted for his failure to obtain in England, since the summer of 1883, photographs showing satisfactory indications of the corona, by the existence in the atmosphere since the autumn of 1883 of finely divided matter which caused an abnormally large amount of glare. Mr. Ray Woods had met the same trouble in Switzerland in the summer of 1884.
In his British Association address, 1891, Prof. Huggins repeated a conclusion which he had expressed in 1885, that the corona is essentially a phenomenon similar in the cause of its formation to the tails of comets—consisting for the most part of matter going from the sun under the action of a force, possibly electrical, which varies as the surface, and can therefore in the case of highly attenuated matter easily master the force of gravity even near the sun—as according with the lines along which thought had been directed by the results of subsequent eclipses.
In the early part of 1868 Prof. Huggins presented to the Royal Society some observations on a small change of refrangibility which he had remarked in a line in the spectrum of Sirius as compared with a line of hydrogen, from which it appeared that the star was moving from the earth with a velocity of about twenty-five miles a second, if the probable advance of the sun in space were taken into account. The thought of discovering motion in this way was not wholly new, though Prof. Huggins was the first to apply it in practice. The Rev. John Mitchell, of the Royal Society, presented an ingenious paper, in 1783, On the Means of discovering the Distance, Magnitude, etc., of the Fixed Stars, in Consequence of the Diminution of the Velocity of their Light, in which he suggested that by the aid of a prism "we might be able to discover diminutions in the velocity of light as perhaps a hundredth, a two-hundredth, a five-hundredth, or even a thousandth part of the whole." Doppler had also, in 1841, suggested that on the same principle on which a sound should become sharper or flatter if there were an approach or a recession between the ear and the source of the sound would apply equally to light; and Fizeau, about eight years later, had pointed out the importance of considering the individual wave-lengths of which white light is composed. Prof. Huggins was not able to continue his observations of this feature till 1872, when, having devised a trustworthy apparatus, and enjoying favorable weather, he applied his method to fourteen stars which were found to have a motion of approach and twelve which appeared to be receding. He remarked upon these results that the velocities of recession or approach assigned to the several stars by him represented the whole of the motion in the line of sight existing between them and the sun. As we know that the sun is moving in space, a part of these observed velocities must be due to the solar motion. He had not attempted to make this correction, because, although the direction of the sun's motion seemed to be satisfactorily ascertained, the velocity with which it was advancing rested on suppositions more or less arbitrary. It would be observed that, speaking generally, the stars which the spectroscope showed to be moving from the earth were situated in a part of the heavens opposite to Hercules, toward which the sun was advancing; while the stars in the neighborhood of that region showed a motion of approach. There were some exceptions to this general statement; and there were some other considerations which appeared to show that the sun's motion in space is not the only, or even in all cases the chief, cause of the observed proper motions of the stars. There could be little doubt that in the observed stellar movements we have to do with two other independent motions, namely, a movement common to certain groups of stars, and a motion peculiar to each star.
Pertaining to other subjects than spectroscopic astronomy on which Prof. Huggins has written, we notice a communication to the Royal Society On the Function of the Sound-post, and on the Proportional Thickness of the Strings of the Violin. A curious letter from him in Nature, in 1873, relates the case of a family of dogs the members of which had inherited an antipathy to butchers' shops and butchers. Some of them could not be induced to pass by a butcher's shop; others showed great uneasiness in the presence of a butcher, although they could not see him; and one of them attacked a gentleman visiting his master, whose business was that of a butcher. In 1872 Dr. Huggins edited and annotated an edition of Schellen's Spectrum Analysis in its Application to Terrestrial Substances and the Physical Constitution of the Heavenly Bodies, translated by Jane and Caroline Lassell.
Dr. Huggins was elected a Fellow of the Royal Society in 1865, and has received two of its medals; he was awarded, with Dr. Miller, the gold medal of the Royal Astronomical Society in 1867, for their conjoint researches, and he was given a second medal of the same society in 1885. He has received doctor's degrees from the Universities of Cambridge, Oxford, Edinburgh, and Trinity College, Dublin; and he holds the honors and memberships of other British societies, and of numerous societies in foreign lands. As Rede lecturer at the University of Edinburgh, in 1869, he gave an account of his researches in astronomy by means of the spectroscope; and as President of the British Association in 1891 he delivered an inaugural address, the more definite purpose of which, as defined by the author, was "not 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 of its more important problems." The success of this effort, the Observatory says, was recognized equally by the general public and by those more familiar with astronomy. "Those who were already familiar with Dr. Huggins and his work have learned afresh almost to their surprise how closely he has been identified with the 'very remarkable discoveries in our knowledge of the heavens which have taken place during this period of thirty years,’ Not that the president materially assists in pointing this moral; rather is it pointed by the facts in spite of him. He is almost too eager to assign credit to others when he might justly have mentioned his own work."
A recent investigation by Mr. Thomas Whitelegge, of Sydney, may cast some light as to the causes which influence marine food supplies. He found that a sudden discoloration of the water in Port Jackson Harbor was caused by the presence of a minute organism which he identified as a species of the genus Glenodinium; and, so far as he was able to judge, fully half of the shore fauna was destroyed by the invaders. The bivalves were almost exterminated wherever the organism was abundant during the whole of the visitation.