News from Hanover put a sudden stop, for a time, to all these labors. The mother wrote, in the utmost distress, to say that DIETRICH had disappeared from his home, it was supposed with the intention of going to India "with a young idler not older than himself." His brother immediately left the lathe at which he was turning an eye-piece in cocoa-nut, and started for Holland, whence he proceeded to Hanover, failing to meet his brother, as he expected. Meanwhile the sister received a letter to say that DIETRICH was "laid up very ill" at an inn in Wapping. ALEXANDER posted to town, removed him to a lodging, and, after a fortnight's nursing, brought him to Bath, where, on his brother WILLIAM'S return, he found him being well cared for by his sister.
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.