ruinous, and overgrown with weeds. Miss Herschel's economical soul was appalled at the price of everything, from coals to butcher's meat; but there were stables where mirrors could be ground; a laundry which would serve for a library, and a grass-plot where the twenty-feet telescope was to be erected. The brother and sister agreed that now they were really in the country they could live on eggs and bacon for next to nothing. Miss Herschel found that she was to be trained for an assistant astronomer, and, "by way of encouragement," as she says, a telescope, adapted for sweeping, was given to her. "I was to sweep for comets, and I see by my journal that I began August, 1782, to record all the remarkable appearances that I saw in my sweeps." She soon had the satisfaction of seeing that her brother was satisfied with her endeavours to assist. It was her business to watch the clock, and note the times of various phenomena; to write down memoranda; to fetch and carry instruments, or to measure the ground with poles. Something of this kind occurred every moment. Measurements on the diameter of the newly-discovered Georgium Sidus, and observations of other planets, double stars, etc., were made with great assiduity. From this time, and for many years, almost the whole of almost every night that was not too cloudy was devoted to observation of the heavens, until daylight sent the astronomers to their beds. But it was soon found that Caroline Herschel must become entirely attached to the writing-desk, so that she seldom had an opportunity, unless in the temporary absence of her brother, for original observation. The use of the twenty-feet telescope was not without its exciting and even dangerous features. Sir William Herschel passed his time principally on a high scaffolding, erected with too impetuous haste to be very safe. A temporary cross-beam represented the safe gallery which would have been erected by a more cautious observer; one night in a high wind the whole affair came to the ground; fortunately, says Miss Herschel, the mirror was uninjured. Shortly afterwards, Miss Herschel herself met with a serious accident. She was sent in haste across ground covered a foot deep with snow to record an observation, but the tube and mirror rested on a temporary contrivance, consisting of a couple of butcher's hooks, one of which penetrated her leg above the knee. In answer to her brother's call to make haste, she could only cry that she was hooked. It was found impossible to raise her without, as she says, leaving nearly two ounces of flesh behind her. It was six weeks before the courageous lady asked for medical advice. Dr. Lind, who came to her assistance, told her that if a soldier had received such a wound he would have been sent for six weeks to hospital. Her principal emotion connected with the event seems to have been satisfaction that her brother lost nothing by the accident, as the remainder of the night was too cloudy to afford intervals favourable for observation.
We mentioned that two great objects were present to Sir William Herschel's mind. The first was to obviate the loss of light consequent on the construction of reflecting telescopes; and we have seen by what simple contrivance the change was effected. In his other object, viz., the manufacture of telescopes, powerful beyond the expectations of previous astronomers, he was equally successful. This is not the place for an examination of the expedients he adopted; it is enough to say that, before the discovery of Uranus, he had applied linear magnifying powers of a thousand, twelve hundred, two thousand two hundred, two thousand six hundred, and even of six thousand times to a reflecting telescope of seven feet in focal length. The Royal Society of London officially requested Herschel to give publicity to the means he had adopted for ascertaining such amounts of magnifying power in his telescopes. His answer is contained in a paper called "Answers to Doubts that might be raised to the High Magnifying Powers used by Herschel," and, as Arago says, the question was settled once for all. In one of his letters to his sister, written in May, 1782, when he first went to London, at the king's desire, to see his Majesty, Herschel says:—
Dr. Maskelyne (the astronomer royal) in public declared his obligations to me for having introduced to them the high powers, for M. Aubert has so much succeeded with them that he says he looks down upon two, three, or four hundred with contempt, and immediately begins with eight hundred, he has used twenty-five hundred very completely, and seen my fine double stars with them.
A month later he writes;—
Among opticians and astronomers nothing is now talked of but what they call my great discoveries. Alas! this shows how far they are behind, when such trifles as I have seen and done are called great. Let me but get at it again! I will make such telescopes and see such things—that is, I will endeavour to do so.
