sumed elements. The latter
numbers are all extremely satisfactory: I am not enough acquainted
with Flamsteed's observations about 1690 to say whether they bear
such an error, but I think it extremely probable.

"'But I should be very glad to know whether this assumed perturbation
will explain the error of the radius vector of _Uranus_. This error
is now very considerable, as you will be able to ascertain by
comparing the normal equations, given in the Greenwich observations
for each year, for the times _before_ opposition with the times
_after_ opposition.'

"I have before stated that I considered the establishment of this
error of the radius vector of _Uranus_ to be a very important
determination. I therefore considered that the trial, whether the
error of radius vector would be explained by the same theory which
explained the error of longitude, would be truly an _experimentum
crucis_. And I waited with much anxiety for Mr. Adams' answer to my
query. Had it been in the affirmative, I should at once have exerted
all the influence which I might possess, either directly, or
indirectly through my friend Professor Challis, to procure the
publication of Mr. Adams' theory.

"From some cause with which I am unacquainted, probably an accidental
one, I received no immediate answer to this inquiry. I regret this
deeply, for many reasons."

[Sidenote: Adams' silence.]

Here we may leave Airy's "account" for a few moments to consider the
reason why he received no answer. Adams was a very shy and retiring young
man, and very sensitive; though capable of a great resolution, and of
enormous perseverance in carrying it out. We know (what is not indicated
in the above account), how steadily he had kept in view the idea of
solving this great problem. It was characteristic of him that as early as
1841 he had formed a resolution to undertake it, although at the time he
was not able to enter upon its accomplishment. The following memorandum,
which is still in existence, having been found among his papers after his
death, records these facts:

"1841, July 3. Formed a design, in the beginning of this week, of
investigating, as soon as possible after taking my degree, the
irregularities in the motion of Uranus, which were as yet unaccounted
for: in order to find whether they may be attributed to the action of