During the ensuing three months, thirty to forty workmen were constantly employed, “some in felling and rooting out trees, some in digging and preparing the ground for the bricklayers who were laying the foundation for the telescope.” “A whole troop of labourers” were, besides, engaged in reducing “the iron tools to a proper shape for the mirror to be ground upon.” Thus, each morning, when dawn compelled Herschel to desist from observation, he found a bevy of people awaiting instructions of all sorts from him. “If it had not been,” his sister says, “for the intervention of a cloudy or moonlit night, I know not when he, or I either, should have got any sleep.” The wash-house was turned into a forge for the manufacture of specially designed tools; heavy articles cast in London were brought by water to Windsor; the library was so encumbered with stores, models, and implements, that “no room for a desk or an atlas remained.”
On July 3rd, 1786, Herschel, accompanied by his brother Alexander, started for Göttingen, commissioned by the King to present to the University one of the ten-foot reflectors purchased from him. He was elected a Member of the Royal Society of Göttingen, and spent three weeks at Hanover with his aged mother, whom he never saw again. During his absence, however, the forty-foot progressed in accordance with the directions he had taken care to leave behind. He trusted nothing to chance. “There is not one screwbolt,” his sister asserted, “about the whole apparatus but what was fixed under the immediate eye of my brother. I have seen him lie stretched many an hour in a burning sun, across the top beam, whilst the iron-work for the various motions was being fixed. At one time no less than twenty-four men (twelve and twelve relieving each other) kept polishing day and night; my brother, of course, never leaving them all the while, taking his food without allowing himself time to sit down to table.”
At this stage of the undertaking it became the fashion with visitors to use the empty tube as a promenade. Dr. and Miss Burney called, in July, 1786, “to see, and take a walk through the immense new telescope.” “It held me quite upright,” the authoress of “Evelina” related, “and without the least inconvenience; so would it have done had I been dressed in feathers and a bell-hoop.”
George III. and the Archbishop of Canterbury followed the general example; and the prelate being incommoded by the darkness and the uncertain footing, the King, who was in front, turned back to help him, saying: “Come, my lord bishop, I will show you the way to heaven.” On another occasion “God save the King” was sung and played within the tube by a large body of musicians; and the rumour went abroad that it had been turned into a ball-room!
The University of Oxford conferred upon Herschel, in 1786, an honorary degree of LL.D.; but he cared little for such distinctions. Miss Burney characterised him as a “man without a wish that has its object in the terrestrial globe;” the King had “not a happier subject.” The royal bounty, she went on “enables him to put into execution all his wonderful projects, from which his expectations of future discoveries are so sanguine as to make his present existence a state of almost perfect enjoyment.” Nor was it possible to “admire his genius more than his gentleness.” Again, after taking tea in his company in the Queen’s lodge: “this very extraordinary man has not more fame to awaken curiosity than sense and modesty to gratify it. He is perfectly unassuming, yet openly happy; and happy in the success of those studies which would render a mind less excellently formed presumptuous and arrogant.” Mrs. Papendick, another court chronicler, says that “he was fascinating in his manner, and possessed a natural politeness, and the abilities of a superior nature.”
His great telescope took rank, before and after its completion, as the chief scientific wonder of the age. Slough was crowded with sightseers. All the ruck of Grand Dukes and Serene Highnesses from abroad, besides royal, noble, and gentle folk at home, flocked to gaze at it and interrogate its maker with ignorant or intelligent wonder. The Prince of Orange was a particularly lively inquirer. On one of his calls at Slough, about ten years after the erection of the forty-foot, finding the house vacant, he left a memorandum asking if it were true, as the newspapers reported, that “Mr. Herschel had discovered a new star whose light was not as that of the common stars, but with swallow-tails, as stars in embroidery?”!
Pilgrim-astronomers came, too—Cassini, Lalande, Méchain and Legendre from Paris, Oriani from Milan, Piazzi from Palermo. Sniadecki, director of the observatory of Cracow, “took lodgings,” Miss Herschel relates, “in Slough, for the purpose of seeing and hearing my brother whenever he could find him at leisure. He was a very silent man.” One cannot help fearing that he was also a very great bore. Von Magellan, another eminent foreign astronomer, communicated to Bode an interesting account of Herschel’s methods of observation. The multitude of entries in his books astonished him. In sweeping, he reported, “he lets each star pass at least three times through the field of his telescope, so that it is impossible that anything can escape him.” The thermometer in the garden stood that night, January 6th, 1785, at 13 deg. Fahrenheit; but the royal astronomer, his visitor remarked, “has an excellent constitution, and thinks about nothing else in the world but the celestial bodies.”
In January, 1787, Herschel made trial with his twenty-foot reflector of the “front-view” plan of construction, suggested by Lemaire in 1732, but never before practically tested. All that had to be done was to remove the small mirror, and slightly tilt the large one. The image was then formed close to the upper margin of the tube, into which the observer, turning his back to the heavens, looked down. The purpose of the arrangement was to save the light lost in the second reflection; and its advantage was at once illustrated by the discovery of two Uranian moons—one (Titania) circling round its primary in about 8¾ hours, the other (Oberon) in 13½ hours. In order to assure these conclusions, he made a sketch beforehand of what ought to be seen on February 10th; and on that night, to his intense satisfaction, “the heavens,” as he informed the Royal Society, “displayed the original of my drawing by showing, in the situation I had delineated them, the Georgian planet attended by two satellites. I confess that this scene appeared to me with additional beauty, the little secondary planets seeming to give a dignity to the primary one which raises it into a more conspicuous situation among the great bodies of our solar system.”
This brilliant result determined him to make a “front-view” of the forty-foot. Its advance towards completion was not without vicissitudes. The first speculum, when put into the tube, February 19th 1787, was found too thin to maintain its shape. A second, cast early in 1788, cracked in cooling. The same metal having been recast February 16th, the artist tried it upon Saturn in October; but the effect disappointing his expectation, he wrought at it for ten months longer. At last, after a few days’ polishing with his new machine, he turned the great speculum towards Windsor Castle; when its high quality became at once manifest. And such was his impatience to make with it a crucial experiment, that—as he told Sir Joseph Banks—he directed it to the heavens (August 28th, 1789) before it had half come to its proper lustre. The stars came out well, and no sooner had he got hold of Saturn than a sixth satellite stood revealed to view! Its “younger brother” was detected September 17th; and the two could be seen, on favourable opportunities, threading their way, like beads of light, along the lucid line of the almost vanished ring. Herschel named them Enceladus and Mimas, and found, on looking up his former observations of Saturn, that Enceladus, the exterior and brighter object, had been unmistakably seen with the twenty-foot, August 19th, 1787. Mimas is a very delicate test of instrumental perfection.
The mirror by which it was first shown measured nearly fifty inches across, and weighed 2,118 pounds. It was slung in a ring, and the sheet-iron tube in which it rested was thirty-nine and a-half feet long and four feet ten inches wide. Ladders fifty feet in length gave access to a movable stage, from which the observer communicated through speaking tubes with his assistants. The whole erection stood on a revolving platform; for the modern equatorial form of mount, by which the diurnal course of the heavens is automatically followed, was not then practically available, and the necessary movements had to be imparted by hand. This involved the attendance of two workmen, but was otherwise less inconvenient than might be supposed, owing to the skill with which the required mechanism was contrived.