About this time another change was made to the house 19 New King Street, which was the last move in Bath. It was here that the Georgium Sidus was discovered.
The music still went on. The oratorios of the Messiah, Judas Maccabeus, and Samson were to be performed under Herschel's direction, with an orchestra of nearly one hundred pieces. The scores and vocal parts of these Carolina copied with her own hands, and the soprani were instructed by her, she being the leading soloist. Along with the music went the astronomy. Not only were new telescopes made, but they were made for immediate use.
The variable star Mira Ceti was observed, and a long series of lunar observations begun.
"In 1779, 1780, and 1781 I measured the heights of about one hundred mountains of the moon, by three different methods.
"Some of these observations are given in Philosophical Transactions, vol. LXX., but most remain uncalculated in my journal till some proper opportunity."[12]
While Herschel was measuring these lunar mountains, in December, 1779, he made by chance an acquaintance of much value to him. Dr. William Watson, a Fellow of the Royal Society, distinguished for his researches in electricity, happened to see him at his telescope, and this led to a visit and an invitation to Herschel to join the Philosophical Society of Bath, then forming. This he gladly did, and it was of use to him in many ways.
He there formed acquaintance with men of his own way of thinking, and he himself became known. Better than all, he learned to measure himself with other men, and by his early papers read to the Society, he gained skill in putting his thoughts before his hearers. This skill he never lost, and the merely literary art of his memoirs would make his papers remarkable without their other merits. He is always clear, and in his early papers especially, he appeals to his particular audience—the Royal Society—in a way which shows that he is conscious of all its weaknesses as well as of its dignity. Later, his tone slightly changed. He became less anxious to win his audience, for he had become an authority. This knowledge lent a quiet strength to his style, but never induced the slightest arrogance of spirit or manner.
The Bath Philosophical Society has left no printed proceedings. Herschel was one of its earliest members, and many papers were communicated to it by his hand. These appear to have been of a very miscellaneous nature. Some of them at least would be of the highest interest to us now.
In the Philosophical Transactions for 1789, p. 220, Herschel tells us that he communicated to that Society "certain mathematical papers" relating to central forces other than the force of gravity, which are or may be concerned in the construction of the sidereal heavens. This early idea was still entertained by Herschel in 1789, and the mathematical papers referred to must be contained in the Minutes of the Society, which on its dissolution were torn from the Minute-book and returned to the writers.
The earliest published writing of Herschel is the answer to the prize question in the "Ladies' Diary" for 1779, proposed by the celebrated Landen, namely: