Somerville and I spent the Christmas at Collingwood with our friends the Herschels. The party consisted of Mr. Airy, Astronomer-Royal, and Mr. Adams, who had taken high honours at Cambridge. This young man and M. Leverrier, the celebrated French astronomer, had separately calculated the orbit of Neptune and announced it so nearly at the same time, that each country claims the honour of the discovery. Mr. Adams told Somerville that the following sentence in the sixth edition of the "Connexion of the Physical Sciences," published in the year 1842, put it into his head to calculate the orbit of Neptune. "If after the lapse of years the tables formed from a combination of numerous observations should be still inadequate to represent the motions of Uranus, the discrepancies may reveal the existence, nay, even the mass and orbit of a body placed for ever beyond the sphere of vision." That prediction was fulfilled in 1846, by the discovery of Neptune revolving at the distance of 3,000,000,000 of miles from the sun. The mass of Neptune, the size and position of his orbit in space, and his periodic time, were determined from his disturbing action on Uranus before the planet itself had been seen.
We left Collingwood as ever with regret.
The following is an extract from a letter written by my mother during this visit:—
FROM MRS. SOMERVILLE TO W. GREIG, ESQ.
Collingwood, 1st January, 1848.
... You can more easily conceive than I can describe the great kindness and affection which we have received from both Sir John and Lady Herschel; I feel a pride and pleasure beyond what I can express in having such friends. Collingwood is a house by itself in the world, there certainly is nothing like it for all that is great and good. The charm of the conversation is only equalled by its variety—every subject Sir John touches turns to doubly refined gold; profound, brilliant, amiable, and highly poetical, I could never end admiring and praising him. Then the children are so nice and he so kind and amusing to them, making them quite his friends and companions.
Yours, my dearest Woronzow,
Most affectionately,
M. Somerville.
We had formed such a friendship with Mr. Faraday that while we lived abroad he sent me a copy of everything he published, and on returning to England we renewed our friendship with that illustrious philosopher, and attended his lectures at the Royal Institution. He had already magnetized a ray of polarised light, but was still lecturing on the magnetic and diamagnetic properties of matter. At the last lecture we attended he showed the diamagnetism of flame, which had been proved by a foreign philosopher. Mr. Faraday never would accept of any honour; he lived in a circle of friends to whom he was deeply attached. A touching and beautiful memoir was published of him by his friend and successor, Professor Tyndall, an experimental philosopher of the very highest genius.