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 CAROLINE HERSCHEL. 307 " I have charge of the moon," said Dr. Herschcl, " but I leave it to my sister to sweep the heavens for comets." But while each had particular and favorite objects, they worked habitually in concert, and they invented a mode of doing this with effect. The great telescope which the king enabled Herschel to construct was set up in the garden of their house. When the night was favorable for' observations, he would muffle himself up in warm clothing and take his seat at the mighty instrument, while she sat in the nearest room, pen in hand, to record his observations. To facilitate the business they had a system of signs and signals of such a nature that the record was made instantaneously and exactly, he having his eye at the telescope, and she hers upon the chronome- ter. This system was the more important, as in England there are only a very few hours in a month when good observations can be taken. If William Herschel was one of the most successful of astronomical explorers he owed very much of his success to the sympathy and the intelligent cooperation of his sister Caroline. It was a common occurrence for her early visitors to be told that " Miss Herschel had been engaged at the telescope all night and had just gone to bed." Besides assisting to produce her brother's catalogue of stars, she published at length a supplementary catalogue of her own, which contained five hundred and sixty stars not previously recorded in similar works. It was pub- lished at the expense of the Royal Society, of which she was afterwards elected a member. Mrs. Somerville and herself were elected members on the same day, two illus- trious ladies, the first of their sex to win this distinction. In 1822 her brother died, leaving one son, John, aged thirty-one. She was then seventy-two years of age. Soon after the death of her brother she went back to her native Hanover, where she lived for the rest of her life 19