ut I interrupted it from Sept. 27th to Feb. 8th. I
believe it was in this Vacation, or in the October term, that I began
every evening to read Thucydides very carefully, as my notes are
marked 1822 and 1823. On August 27 I find that I was reading Ovid's
Fasti.

"In Mathematics I find the equation x + y = a, x^q + y^q = b,
Caustics, Calculus of Variations, Partial Differentials, Aberration of
Light, Motions of Comets, various Optical constructions computed with
spherical aberrations, Particular Solutions, Mechanics of Solid
Bodies, Attractions of Shells, Chances, Ivory's attraction-theorem,
Lunar Theory (algebraical), Degrees across meridian, theoretical
refraction, Newton's 3rd Book, Investigation of the tides in a shallow
equatoreal canal, from which I found that there would be low-water
under the moon, metacentres, rotation of a solid body round three
axes, Attractions of Spheroids of variable density, finite
differences, and complete Figure of the Earth. There is also a good
deal of investigation of a mathematical nature not connected with
College studies, as musical chords, organ-pipes, sketch for a
computing machine (suggested by the publications relating to
Babbage's), sketch of machine for solving equations. In August there
is a plan of a MS. on the Differential Calculus, which it appears I
wrote then: one on the Figure of the Earth written about August 15th;
one on Tides, Sept. 25th; one on Newton's Principia with algebraical
additions, Nov. 1st. On Sept. 6th and 10th there are Lunar Distances
observed with Rothman's Sextant and completely worked out; for these I
prepared a printed skeleton form, I believe my first. On December 13th
there are references to books on Geology (Conybeare and Phillips, and
Parkinson) which I was beginning to study. On July 27th, being the day
on which I completed my 21st year, I carefully did nothing.

"Another subject partly occupied my thoughts, which, though not (with
reference to practical science) very wise, yet gave me some Cambridge
celebrity. In July 1819 I had (as before mentioned) sketched a plan
for constructing reflecting telescopes with silvered glass, and had
shewn it afterwards to Mr Peacock. I now completed the theory of this
construction by correcting the aberrations, spherical as well as
chromatic. On July 13th, 1822, I drew up a paper about it for Mr
Peacock. He approved it much, and in some way communicated it to Mr
(afterwards Sir John) Herschel. I was soon aft