professed to give a mathematical
explanation of the Trinity, see farther on.--S. E. De M.

[554] Sabellius (fl. 230 A.D.) was an early Christian of Libyan origin. He
taught that Father, Son, and Holy Spirit were different names for the same
person.

[555] Sir Richard Phillips was born in London in 1767 (not 1768 as stated
above), and died there in 1840. He was a bookseller and printer in
Leicester, where he also edited a radical newspaper. He went to London to
live in 1795 and started the _Monthly Magazine_ there in 1796. Besides the
works mentioned by De Morgan he wrote on law and economics.

[556] It was really eighteen months.

[557] While he was made sheriff in 1807 he was not knighted until the
following year.

[558] James Mitchell (c. 1786-1844) was a London actuary, or rather a
Scotch actuary living a good part of his life in London. Besides the work
mentioned he compiled a _Dictionary of Chemistry, Mineralogy, and Geology_
(1823), and wrote _On the Plurality of Worlds_ (1813) and _The Elements of
Astronomy_ (1820).

[559] Richarda Smith, wife of Sir George Biddell Airy (see note 129, page
85) the astronomer. In 1835 Sir Robert Peel offered a pension of L300 a
year to Airy, who requested that it be settled on his wife.

[560] Mary Fairfax (1780-1872) married as her second husband Dr. William
Somerville. In 1826 she presented to the Royal Society a paper on _The
Magnetic Properties of the Violet Rays of the Solar Spectrum_, which
attracted much attention. It was for her _Mechanism of the Heavens_ (1831),
a popular translation of Laplace's _Mecanique Celeste_, that she was
pensioned.

[561] Dominique Francois Jean Arago (1786-1853) the celebrated French
astronomer and physicist.

[562] For there is a well-known series

1 + 1/2^2 + 1/3^2 + ... = [pi]^2/6.

If, therefore, the given series equals 1, we have

2 = 1/6 [pi]^2

or [pi]^2 = 12,

whence [pi] = 2 [root]3.

But c = [pi]d, and twice the diagonal of a cube on the diameter is 2d
[root]3.

[563] There was a second edition in 1821.

[564] London, 1830.

[565] He was a resident of Chatham, and seems to have published no other
works.

[566] Richard Whately (1787-1863) was, as a child, a calculating prodigy
(see note 132, page 86), but lost the power as is usually the case with
well-balanced minds. He was a fellow of Oriel College, Oxford, and in 1825
became principal of St. Alban Hall. He was a friend of Newman, Keble, and
others