Sir William Herschel: His Life and Works Part 8

"_Aug. 11th_, _12th_, _13th_, and _14th_ [1822], I went as usual to spend some hours of the forenoon with my brother.

"_Aug. 15th._--I hastened to the spot where I was wont to find him, with the newspaper which I was to read to him. But instead I found Mrs. MONSON, Miss BALDWIN, and Mr. BULMAN, from Leeds, the grandson of my brother's earliest acquaintance in this country. I was informed my brother had been obliged to return to his room, whither I flew immediately. Lady H. and the housekeeper were with him, administering everything which could be thought of for supporting him. I found him much irritated at not being able to grant Mr.

BULMAN'S request for some token of remembrance for his father. As soon as he saw me, I was sent to the library to fetch one of his last papers and a plate of the forty-foot telescope. But for the universe I could not have looked twice at what I had s.n.a.t.c.hed from the shelf, and when he faintly asked if the breaking up of the Milky Way was in it, I said 'Yes,' and he looked content. I cannot help remembering this circ.u.mstance; it was the last time I was sent to the library on such an occasion. That the anxious care for his papers and workrooms never ended but with his life, was proved by his frequent whispered inquiries if they were locked and the key safe, of which I took care to a.s.sure him that they were, and the key in Lady HERSCHEL'S hands.

"After half an hour's vain attempt to support himself, my brother was obliged to consent to be put to bed, leaving no hope ever to see him rise again."

On the 25th of August, 1822, HERSCHEL died peacefully at the age of eighty-four years.

His remains lie in the little church at Upton, near Windsor, where a memorial tablet has been erected by his son. The epitaph is as follows:[30]

H. S. E.

GULIELMUS HERSCHEL Eques Guelphicus Hanoviae natus Angliam elegit patriam Astronomis aetatis suae praestantissimis Merito annumeratus Ut leviora sileantur inventa Planetam ille extra Saturni orbitam Primus detexit Novis artis adjumentis innixus Quae ipse excogitavit et perfecit Coelorum perrupit claustra Et remotiora penetrans et explorans spatia Incognitos astrorum ignes Astronomorum oculis et intellectui subjecit Qua sedulitate qua solertia Corporum et phantasmatum Extra systematis nostri fines lucentium Naturam indagaverit Quidquid paulo audacius conjecit Ingenita temperans verecundia Ultro testantur hodie aequales Vera esse quae docuit pleraque Siquidem certiora futuris ingeniis subsidia Debitura est astronomia Agnoscent forte posteri Vitam utilem innocuam amabilem Non minus felici laborum exitu quam virtutibus Ornatam et vere eximiam Morte suis et bonis omnibus deflenda Nec tamen immatura clausit Die XXV Augusti A. D. CI[C]I[C]CCCXXII aetatis vero suae Lx.x.xIV.

FOOTNOTES:

[18] BODE'S _Jahrbuch_, 1788, p. 144.

[19] ZACH'S _Monatlich Correspondenz_, 1802, p. 56.

[20] BODE'S _Jahrbuch_, 1788, p. 161.

[21] Through Sir JOHN HERSCHEL there is preserved to us an incident of his early boyhood, which shows the nature of the training his young mind received in the household at Slough.

Walking with his father, he asked him "What was the oldest of all things?" The father replied, after the Socratic manner, "And what do you suppose is the oldest of all things?" The boy was not successful in his answers, whereon the old astronomer took up a small stone from the garden walk: "There, my child, there is the oldest of all the things that I certainly know." On another occasion the father asked his son, "What sort of things do you think are most alike?" The boy replied, "The leaves of the same tree are most like each other." "Gather, then, a handful of leaves from that tree," rejoined the philosopher, "and choose two which are alike."--_Monthly Notices Royal Astronomical Society_, vol. x.x.xii., page 123.

[22] _Memoir of CAROLINE HERSCHEL_, p. 42.

[23] "Of late years these expectations have been more than accomplished by the discovery of no fewer than four planetary bodies, almost all in the same place; but so small that Dr. HERSCHEL refuses to honor them with the name of planets, and chooses to call them asteroids, though for what reason it is not easy to determine, unless it be to deprive the discoverers of these bodies of any pretence for rating themselves as high in the list of astronomical discoverers as himself."--_History of the Royal Society_, by THOMAS THOMSON, p. 358.

This work was published in 1812, and therefore during the lifetime of HERSCHEL.

[24] _Poetical History of Astronomy_: this work was nearly completed, but was never published. The whole of it was read to HERSCHEL, in order that BURNEY might have the benefit of his criticism on its technical terms.

[25] _Memoirs of Dr. BURNEY_, vol. iii., p. 264.

[26] Life and Letters of THOMAS CAMPBELL, edited by WILLIAM BEATTIE, vol. ii., p. 234.

[27] This interview must have taken place in 1802, during HERSCHEL'S journey to Paris. We have no other record of it.

[28] The will of HERSCHEL was dated December 17th, 1818.

"The personal effects were sworn under 6,000. The copyhold and other lands and tenements at Upton-c.u.m-Chalvey, in the County of Bucks, and at Slough, he decrees to his son, with 25,000 in the 3 per cent. Reduced Annuities. 2,000 are given to his brother JOHANN DIETRICH, and annuities of 100 each to his brother JOHANN ALEXANDER and to his sister CAROLINA; 20 each to his nephews and nieces, and the residue (with the exception of astronomical instruments, telescopes, observations, etc., which he declares to have given, on account of his advanced age, to his son for the purpose of continuing his studies) is left solely to Lady HERSCHEL."--_Gentleman's Magazine_, vol. xcii., 1822, p. 650.

It is not necessary to say here how n.o.bly Sir JOHN HERSCHEL redeemed the trust confided in him. All the world knows of his Survey of the Southern Heavens, in which he completed the review of the sky which had been begun and completed for the northern heavens by the same instruments in his father's hands. A glance at the Bibliography at the end of this book will show the t.i.tles of several papers by Sir JOHN, written with the sole object of rendering his father's labors more complete.

[29] He was created a knight of the Royal Hanoverian Guelphic Order in 1816, and was the first President of the Royal Astronomical Society in 1821, his son being its first Foreign Secretary.

[30] BODE'S _Jahrbuch_, 1823, p. 222.

CHAPTER IV.

REVIEW OF THE SCIENTIFIC LABORS OF WILLIAM HERSCHEL.

In this chapter I shall endeavor to give such explanations as will enable the general reader to follow the course of discovery in each branch of astronomy and physics, regularly through the period of HERSCHEL'S life, and up to the state in which he left it.

A more detailed and precise account, which should appeal directly to the professional astronomer, will not be needed, since ARAGO has already fulfilled this want in his "_a.n.a.lyse de la vie et des travaux de Sir WILLIAM HERSCHEL_," published in 1842. The few misconceptions there contained will be easily corrected by those to whom alone they are of consequence. The latter cla.s.s of readers may also consult the abstracts of HERSCHEL'S memoirs, which have been given in "_A Subject-index and a Synopsis of the Scientific Writings of Sir WILLIAM HERSCHEL_," prepared by Dr. HASTINGS and myself, and published by the Smithsonian Inst.i.tution.

An accurate sketch of the state of astronomy in England and on the Continent, in the years 1780-1820, need not be given. It will be enough if we remember that of the chief observatories of Europe, public and private, no one was actively devoted to such labors as were undertaken by HERSCHEL at the very beginning of his career.

His observations on variable stars, indeed, were in the same line as those of PIGOTT; FLAUGERGUES and DARQUIER, in France, had perhaps preceded him in minute scrutiny of the sun's surface, etc.; but, even in that department of observation, he at once put an immense distance between himself and others by the rapid and extraordinary advances in the size and in the excellence of his telescopes. Before his time the princ.i.p.al aids to observation were the Gregorian and Newtonian telescopes of SHORT, and the small achromatics of DOLLOND.[31]

We have seen, in what goes before, how his patient zeal had succeeded in improving upon these. There was no delay, and no rest. Steadily the art of making reflectors was urged forward, until he had finally in his hands the forty-foot telescope.

It must be admitted that this was the limit to which the manufacture of powerful telescopes could be pushed in his generation. The optical and mechanical difficulties which prevented a farther advance required time for their solution; and, indeed, some of these difficulties are scarcely solved at this day. It may fairly be said that no reflector larger than three feet in aperture has yet realized our expectations.

_The Improvement of Telescopes and Optical Apparatus._

It will be of interest to give in this place some connected account of the large forty-foot reflector, of four feet aperture, made by HERSCHEL.

Its history extends from 1785 to 1811. Its manufacture was considered by his cotemporaries as his greatest triumph. As a machine, it was extremely ingenious in all its parts, as may be seen from the elaborate description and plates of it published in the _Philosophical Transactions_ for 1795. One of its mirrors certainly had good definition, for, by means of it, the two small satellites of _Saturn_ (_Mimas_ and _Enceladus_) were discovered, and these discoveries alone would make it famous. Perhaps more was expected of it by the public in general than it absolutely performed. Its merits were after a while decried, and HERSCHEL even felt obliged to state why he did not always employ it in his observations. His reasons were perfectly valid, and such as any one may understand. The time required to get so large a machine into working order was a serious tax; it required more a.s.sistants than his twenty-foot telescope, and he says, "I have made it a rule never to employ a larger telescope when a smaller will answer the purpose."

It still remains as a remarkable feat of engineering and an example of great optical and mechanical skill. It led the way to the large reflectors of Lord ROSSE, some sixty years later, and several of the forty-foot telescopes of the present day even have done less useful work. Its great feat, however, was to have added two satellites to the solar system. From the published accounts of it the following is taken:

"When I resided at Bath I had long been acquainted with the theory of optics and mechanics, and wanted only that experience so necessary in the practical part of these sciences. This I acquired by degrees at that place, where in my leisure hours, by way of amus.e.m.e.nt, I made several two-foot, five-foot, seven-foot, ten-foot, and twenty-foot Newtonian telescopes, beside others, of the Gregorian form, of eight, twelve, and eighteen inches, and two, three, five, and ten feet focal length. In this way I made not less than two hundred seven-foot, one hundred and fifty ten-foot, and about eighty twenty-foot mirrors, not to mention the Gregorian telescopes.[32]

"The number of stands I invented for these telescopes it would not be easy to a.s.sign. . . . In 1781 I began to construct a thirty-foot aerial reflector, and having made a stand for it, I cast the mirror thirty-six inches in diameter. This was cracked in cooling. I cast it a second time, and the furnace I had built in my house broke."

Soon after, the Georgian planet was discovered, and this interrupted the work for a time.

"In the year 1783 I finished a very good twenty-foot reflector with a large aperture, and mounted it upon the plan of my present telescope. After two years' observation with it, the great advantage of such apertures appeared so clearly to me that I recurred to my former intention of increasing them still further; and being now sufficiently provided with experience in the work which I wished to undertake, the President of the Royal Society, who is always ready to promote useful undertakings, had the goodness to lay my design before the king. His Majesty was graciously pleased to approve of it, and with his usual liberality to support it with his royal bounty.

"In consequence of this arrangement I began to construct the forty-foot telescope about the latter end of 1785.[33] The woodwork of the stand and machines for giving the required motions to the instrument were immediately put in hand. In the whole of the apparatus none but common workmen were employed, for I made drawings of every part of it, by which it was easy to execute the work, as I constantly inspected and directed every person's labor; though sometimes there were not less than forty different workmen employed at the same time. While the stand of the telescope was preparing, I also began the construction of the great mirror, of which I inspected the casting, grinding, and polis.h.i.+ng, and the work was in this manner carried on with no other interruption than that occasioned by the removal of all the apparatus and materials from where I then lived, to my present situation at Slough.

"Here, soon after my arrival, I began to lay the foundation upon which by degrees the whole structure was raised as it now stands, and the speculum being highly polished and put into the tube, I had the first view through it on February 19, 1787. I do not, however, date the completing of the instrument till much later. For the first speculum, by a mismanagement of the person who cast it, came out thinner on the centre of the back than was intended, and on account of its weakness would not permit a good figure to be given to it.

"A second mirror was cast January 26, 1788, but it cracked in cooling. February 16 we recast it, and it proved to be of a proper degree of strength. October 24 it was brought to a pretty good figure and polish, and I observed the planet _Saturn_ with it. But not being satisfied, I continued to work upon it till August 27, 1789, when it was tried upon the fixed stars, and I found it to give a pretty sharp image. Large stars were a little affected with scattered light, owing to many remaining scratches on the mirror.

August the 28th, 1789, having brought the telescope to the parallel of _Saturn_, I discovered a _sixth_ satellite of that planet, and also saw the spots upon _Saturn_ better than I had ever seen them before, so that I may date the finis.h.i.+ng of the forty-foot telescope from that time."

Another satellite of _Saturn_ was discovered with the forty-foot on the 17th of September (1789). It was used for various observations so late as 1811. On January 19, of that year, HERSCHEL observed the nebula of _Orion_ with it. This was one of his last observations.

The final disposition of the telescope is told in the following extract from a letter of Sir JOHN HERSCHEL'S to Mr. WELD, Secretary of the Royal Society:

"COLLINGWOOD, _March 13, 1847_.

. . . "In reply to your queries, respecting the forty-foot reflecting telescope constructed by my father, I have to state that King GEORGE III. munificently defrayed the _entire_ cost of that instrument (including, of course, all preparatory cost in the nature of construction of tools, and of the apparatus for casting, grinding, and figuring the reflectors, of which two were constructed), at a total cost of 4,000. The woodwork of the telescope being so far decayed as to be dangerous, in the year 1839 I pulled it down, and piers were erected on which the tube was placed, _that_ being of iron and so well preserved, that, although not more than one-twentieth of an inch thick, when in the horizontal position it sustained within it all my family, and continues to sustain inclosed within it, to this day, not only the heavier of the two reflectors, but also all the more important portions of the machinery. . . .