NUMERICAL LUNAR THEORY.

_1890, Sept. 29_.

I had made considerable advance (under official difficulties) in
calculations on my favourite Numerical Lunar Theory, when I discovered
that, under the heavy pressure of unusual matters (two Transits of
Venus and some eclipses) I had committed a grievous error in the first
stage of giving numerical value to my Theory.

My spirit in the work was broken, and I have never heartily proceeded
with it since.

G.B. AIRY.

Probably the error referred to here is the suspected error mentioned
above in his Report of 1878, as to which he subsequently became more
certain.

Whatever may be the imperfections of the Numerical Lunar Theory, it is
a wonderful work to have been turned out by a man 85 years old. In its
idea and inception it embodies the experience of a long life actively
spent in practical science. And it may be that it will yet fulfil the
objects of its author, and that some younger astronomer may take it
up, correct its errors (wherever they may be), and fit it for
practical use. And then the labour bestowed upon it will not have
been in vain.

Subject always to the absorbing occupations of the Lunar Theory he
amused himself with reading his favourite subjects of History and
Antiquities. His movements during the remainder of the year 1881 were
as follows: In September he paid a two days' visit to Lady Herschel at
Hawkhurst. From Oct. 4th to 17th he was at the Cumberland Lakes and
engaged in expeditions in the neighbourhood. From Nov. 5th to 8th he
was at Cambridge, inspecting Prof. Stuart's workshops, and other
scientific institutions. On Dec. 13th he went to Playford.--Amongst
miscellaneous matters: in November he wrote to Mr Rothery on the loss
of the 'Teuton' at some length, with suggestions for the safer
construction of such vessels.--In October he was asked for suggestions
regarding the establishment of a "Standard Time" applicable to the
railway traffic in the United States: he replied as follows:

_1881, Oct. 31_.

SIR,

I have to acknowledge your letter of October 17, introducing to my
notice the difficulty which appears to be arising in America regarding
a "Standard Time," for extensive use throughout N. America
"applicable to railway traffic only." The subject, as including