mbination 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