SIR JOHN FREDERICK WILLIAM HERSCHEL, BART. (1792-1871), the illustrious astronomer, the only son of Sir F. William Herschel, was born at Slough, Bucks, in the year 1792. His early home was a singular one, and eminently adapted to nurture into greatness any child born, as he was, with natural gifts capable of wide development. The examples about him were those of silent but ceaseless industry, busied about things which, at the first view, seemed to have no apparent connexion with the world outside the walls of his abode, but which, at a mature period of his life, he, with rare eloquence, taught his countrymen to appreciate as foremost among those influences which satisfy and exalt the nobler instincts of our nature.
His scholastic education commenced at Eton, but maternal fears or prejudices soon removed him to the house of a private tutor. Thence, at the early age of seventeen, he was sent to St John's College, Cambridge, and the form and method of the mathematical instruction he there received exercised a material influence on the whole complexion of his scientific career. In due time the young student acquired the highest academical distinction of his year, graduating as senior wrangler. It was during his undergraduateship that he and two of his fellow-students who subsequently attained to very high eminence in their respective careers of life, Dean Peacock and Mr Babbage, entered into a sort of moral compact that they would "do their best to leave the world wiser than they found it,"a compact loyally and successfully carried out by all three to the end. As a commencement of this laudable attempt we find Herschel associated with these two friends in the production of a work on the differential calculus, and on cognate branches of mathematical science, which changed the whole style and aspect of mathematical learning in England, and brought it up to the level of the Continental methods. Two or three memoirs communicated to the Royal Society on new applications of mathematical analysis at once placed him in the front rank of the cultivators of this branch of knowledge. Of these his father had the gratification of introducing the first, but the others were presented in his own right as a fellow.
His first intention had been to study for the bar, and with this view he left the university, and placed himself under the guidance of an eminent special pleader of that day. Probably this temporary choice of a profession arose from the extraordinary success which for some time had attended the efforts of so many eminent Cambridge mathematicians in legal pursuits. Be that as it may, an early acquaintance with Dr Wollaston in London soon changed the direction of his studies. In 1820, assisted by his father, he completed a mirror of 18 inches diameter and 20 feet focal length, for a reflecting telescope. This, subsequently improved by his own hands, became the instrument which enabled him to effect the astronomical observations which, more than any other of his great works, form the basis of his fame. In 1821-23 we find him associated with Mr South in the re-examination of his father's double stars, by the aid of an achromatic telescope and other appliances, the like of which for excellence and power had not hitherto been collected. For this work in 1826 he received the recognition of the Astronomical Society by the award of their gold medal; the French Institute also presented him with the Lalande medal for the same contribution to astronomical science. It ought also to be mentioned that in 1821 the Royal Society had presented him with the Copley medal for his mathematical contributions to their Transactions. From 1824 to 1827 he held the distinguished and responsible post of secretary to that society. In 1827 he was elected to the chair of the Astronomical Society, which office he also filled on two subsequent occasions. In the course of the discharge of his important offices in the last-named society he ennobled its literature by his memorable presidential addresses and obituary notices of deceased fellows, which, it is not too much to say, are, by their combination of eloquence and wisdom, the chief adornments of their printed memoirs. In 1831 the honour of knighthood was conferred on him by William IV., and two years later he again received the recognition of the Royal Society by the award of one of their medals for his memoir " On the Investigation of the Orbits of Revolving Double Stars." There is a significance in this award ; the father had been the original discoverer of the extension of gravitation to the remotest boundaries of the visible universe, and the son had now put the crowning stone to this edifice of discovery by the invention of a graphical method whereby the eye could as it were see the two component stars of the binary system revolving before it, after the regularity of the Newtonian law.
Before the end of the year 1833, being then about forty years of age, Sir John Herschel had re-examined all his father's discoveries of double stars and nebulas, and had added many similar bodies to his own list; this alone constituted a gigantic work even for the lifetime of any astronomer in that day. For it should be remembered that the astronomer was not as yet provided with those curious and valuable automatic contrivances for observing and for recording observations which at present most materially abridge the labour and increase the accuracy of astronomical work such as that in which Sir John had been engaged. And he had no assistant. Equatorial clocks for turning the telescope, electrical chronographs for recording the times of the phenomena observed, were at that date unknown.
His scientific life now entered another and very characteristic phase. The bias of his mind, as he subsequently was wont to declare, was towards chemistry and the phenomena of light, rather than towards astronomy. Indeed, very shortly after taking his academical degree at Cambridge, he proposed himself as a candidate for the vacant chair of chemistry in that university ; but, as he said with some humour, the result of the election was that of the votes he had a glorious minority of one. In fact Herschel had become an astronomer from a sense of duty, just as his father had become one by fascination and fixed resolve; hence it was by filial loyalty to his father's memory that he was now impelled to undertake the completion of that work which at Slough had been so grandly commenced. William Herschel had explored the northern heavens ; John Herschel determined to explore the heavens of the south, as well as re-explore the north. " I resolved," he said, " to attempt the completion of a survey of the whole surface of the heavens ; and for this purpose to trausport into the other hemisphere the same instrument which had been employed in this, so as to give a unity to the results of both portions of the survey, and to render them comparable with each other." In accordance with this resolution, he and his family embarked for the Cape on the 13th November 1833; they arrived in Table Bay on the 15th January 1834 ; and proceedings, he says, "were pushed forward with such effect that on the 22d of February I was enabled to gratify my curiosity by a view of « Crucis, the nebula about r¡ Argus, and some other remarkable objects in the 20-foot reflector, and on the night of the 4th of March to commence a regular course of sweeping."
To give an adequate description of the vast mass of labour completed during the next four busy years of his life at Feldhausen would require the transcription of a considerable portion of the Cape Observations, a volume which probably is not surpassed in varied interest or astronomical importance by any scientific work in existence; although it might perhaps be equalled by a judicious selection from Sir William's " Memoirs," now scattered in some thirty volumes of the Philosophical Transactions. It was published, at the sole expense of the late duke of Northumberland, but not till 1847, nine years after the author's return to England, for the very cogent reasons assigned by himself:"The whole of the observations, as well as the entire work of reducing, arranging, and preparing them for the press, have been executed by myself." There are 164 pages of catalogues of southern nebula; and clusters of stars. There are then careful and elaborate drawings of the southern appearance of the great nebula in Orion, and of the region surrounding the remarkable star of Argo. The labour and the thought bestowed upon some of these objects are almost incredible ; several months were well spent upon a minute spot in the heavens containing 1216 stars, but which an ordinary spangle, held at a distance of an arm's length, would eclipse. These catalogues and charts being completed, he proceeds to discuss their significance, which in the eyes of science possesses an absorbing interest. He confirms his father's hypothesis that these wonderful masses of glowing vapours are not irregularly scattered, and without apparent law, hither and thither in the visible heavens, but are collected in a sort of canopy, whose vertex is at the pole of that vast stratum of stars in which our solar system finds its position,buried in it, as he supposes, at a depth not greater than that of the average distance from us of an eleventh magnitude star. Then follows his catalogue of the relative positions and magnitudes of the southern double stars. And he applies to one of them, y Virginia, that beautiful graphical method invented by himself, whereby he determines the orbit of the two components round each other ; and he had the satisfaction of witnessing with his own eyes the fulfilment of a prediction he had made some years before, viz., that the two stars would, in the course of their orbital movements, appear to close up into a single star, inseparable by any telescopic power. The double stars and their stately revolutions and lustrous colours dismissed, in the next chapter he proceeds to describe the observations which he had made on their varying and relative brightness, It has been already detailed how his i'ather commenced his scientific career by similar observations on the varying magnitudes of many stars, and how his remarks culminated years afterwards in the question whether the variation of the lustre of our sun, by the presence or absence of sun spots, affected our harvests and the price of corn. The son carries his speculations backwards to a still more philosophical depth. The variation from time to time, he remarks, in the lustre of our sun, to the extent of half a magnitude, would account for those strange alternations of a semi-arctic and semi-tropical climate which geological researches have disclosed as having occurred in various regions of our globe.
Herschel returned to his English home in the spring of 1838. As was natural and honourable to all concerned, he Was welcomed with an enthusiastic greeting. By the queen at her coronation he was created a baronet; and, what to him was better than all such rewards, other men caught the contagion of his example, and laboured in fields similar to his own, with an adequate portion of his success. In particular Mr Lassell transported a telescope as large as the celebrated Herschelian telescope to Malta, where with excellent results he "minded the heavens" for the space of four years. He was rewarded there, and at his own English residence near Liverpool, by the discovery of new satellites of Saturn and of Uranus, constituting what Sir John Herschel, animated by a fraternal sympathy, well called an epoch in astronomy. Mr De La Rue also, at Islington and at Cranford, followed zealously and successfully in the wake of the same infectious enthusiasm.
Herschel was a highly accomplished chemist. His discovery of the solvent power of hyposulphite of soda on the otherwise insoluble salts of silver, in 1819, exercised a most important influence on the practical applications of photography twenty years afterwards ; and in 1839, the natal era of that valuable art, he, independently of Mr Fox Talbot, had discovered the means of taking and multiplying photographic pictures, and early in the spring of that year exhibited more than twenty photographic pictures to the Royal Society, including one of the old 40-foot telescope. He was the first person to introduce the now well-known terms positive and negative in photographic images, and to deposit upon glass a sensitized film for the reception of the picture. He also paved the way for Professor Stokes's important discovery of the change which luminous waves may suffer in their period of oscillation, by his addition of the lavender rays to the spectrum, and by his announcement of "epipolic dispersion," as exhibited by sulphate of quinine. Several other important and successful researches ot his, connected with the undulatory theory of light, are scattered through the pages of his treatise on " Light" published in the Encyclopaedia Metropolitana.
To the other varied accomplishments of his gifted mind we must add the graces of a deep poetic feeling. Perhaps no man can become a truly great mathematician or great philosopher, if unendowed with the versatile powers of the imagination. John Herschel possessed this endowment to a large extent; and he had reserved for himself as a solace and enjoyment in old age the translation of the Iliad into verse. He had at an earlier period of life translated in a similar manner Schiller's Walk. But the main work of his declining years was the collection of all his father's catalogues, combined with his own observations and those of other astronomers of nebulae and double stars, each into a single volume. He lived to complete the former, and to present it to the Royal Society, who have published it in a separate form in the Philosophical Transactions. The latter work he had not fully completed at his death ; but he bequeathed as much of it as was finished to the Astronomical Society. That society has printed a portion of it, which serves as an index to the observations of various astronomers on double stars up to the year 1866.
A complete list of his various contributions to learned societies will be found in the Royal Society's great catalogue, and from them may be gathered most of the records of his busy scientific life. Sir John Herschel met with an amount of public recognition which was unusual in the time of his illustrious father. Naturally he was a member of almost every important learned society in both hemispheres. For five years he held the office of master of the mint, the same appointment which, more than a century before, had been occupied by Sir Isaac Newton; his friends also offered to propose him as president of the Royal Society and again as a member of parliament for the university of Cambridge, but neither office was within the scope of his own desires.
ln private life Sir John Herschel was a firm and most active friend ; he had no jealousies ; he avoided all scientific feuds ; he gladly accorded a helping hand to those who consulted him in scientific difficulties ; he never discouraged, and still less disparaged, men younger than or inferior to himself ; he was pleased when his own work was appreciated, but that was never an object of his solicitude : it was said of him by a discriminating critic, and without extravagance, that " his was a life full of the serenity of the sage and the docile innocence of a child."
He died at Collingwood, his residence near Hawkhurst in Kent, May 11, 1871, in the seventy-ninth year of his age, and his remains are interred in Westminster Abbey close to the grave of Sir Isaac Newton.
Sir John Herschel, independently of the labours connected with his Cape Observations, was the author of several books, one of which at least, On the Study of Natural Philosojihy (1830), possesses an interest which no future advances of the subjects on which he wrote can obliterate from the attention of thoughtful men in any age. in 1849 came the Outlines of Astronomy, of which it is enough to say that, notwithstanding the obvious disadvantage arising from the practice of stereotyping textbooks which relate to progressive sciences, there is no more instructive volume extant on the subject of which it treats. His articles, " Meteorology," " Physical Geography," and "Telescope," contributed to the 8th edition of the Encyclopaedia Britannica, were afterwards published separately. There is also another very valuable little book, which originated from a happy peculiarity of Sir John Herschel's dignified simplicity and truthfulness of mind. When he was at the Cape he more than once assisted in the attempts there made to diffuse a love of knowledge among men not engaged in literary pursuits. In one of his addresses he, with a kindly and far-seeing wisdom, told his audience that the advance of a nation's intelligence or a nation's fame did not depend upon a few successful philosophers toiling in their lonely studies, and gathering great reputations for their learning or their discoveries, but that a nation's progress rather lay in the diffusion of their knowledge among the masses of the population. Acting practically on this principle, he, on his return to England, published, in Good Worals and elsewhere, a series of papers on interesting points of natural philosophy, which have since been collected in a volume called Familiar Lectures on Scientific Subjects. None but a deep thinking philosopher could have written this book ; none but a clear thinking master of his subjects could have made it what it is, enticingly intelligible. Another volume of his, not so widely known to the public as any of the above works, is his Collected Addresses, in which he is seen in his happiest and most instructive mood, walking, as it were, at liberty among sympathizing associates, in his own fields, and enamoured of their beauties. (C. P.)