lly putting me on a fair
footing in this matter. I returned by Holyhead, and arrived at
Birmingham on Apr. 23rd. While waiting there and looking over some
papers relating to the spherical aberration of eye-pieces, in which I
had been stopped some time by a geometrical difficulty, I did in the
coffee-room of a hotel overcome the difficulty; and this was the
foundation of a capital paper on the Spherical Aberration of
Eye-pieces. This paper was afterwards presented to the Cambridge
Philosophical Society.

"About this time a circumstance occurred of a disagreeable nature,
which however did not much disconcert me. Mr Ivory, who had a good
many years before made himself favourably known as a mathematician,
especially by his acquaintance with Laplace's peculiar analysis, had
adopted (as not unfrequently happens) some singular hydrostatical
theories. In my last Paper on the Figure of the Earth, I had said that
I could not receive one of his equations. In the Philosophical
Magazine of May he attacked me for this with great heat. On May 8th I
wrote an answer, and I think it soon became known that I was not to be
attacked with impunity.

"Long before this time there had been some proposal about an excursion
to the Lake District with my sister, and I now arranged to carry it
out. On May 23rd I went to Bury and on to Playford: while there I
sketched the Cumberland excursion. On June 5th I went to London, I
believe to the Visitation of the Greenwich Observatory to which I was
invited. I also attended the meeting of the Board of Longitude. I
think it was here that Pond's Errors of the Sun's place in the
Nautical Almanac from Greenwich Observations were produced. On June
7th I went by coach to Rugby, where I met my sister, and we travelled
to Edensor. We made a number of excursions in Derbyshire, and then
passed on by Penrith to Keswick, where we arrived on June 22nd. From
Keswick we made many excursions in the Lake District, visited Mr
Southey and Mr Wordsworth, descended a coal mine at Whitehaven, and
returned to Edensor by the way of Ambleside, Kendal, and Manchester.
With sundry excursions in Derbyshire our trip ended, and we returned
to Cambridge on the 21st July.

"During this Long Vacation I had one private pupil, Crawford, the only
pupil this year, and the last that I ever had. At this time there is
on my papers an infinity of optical investigations: also a plan of an
eye-piece with a concave lens to destroy certain aberra