self, for there were very few so perfectly free from vanity and
affectation. To this circumstance may be attributed a peculiarity of
manner in the mode in which he communicated information to those
who sought it from him, which was to many extremely disagreeable. He
usually, by a few questions, ascertained precisely how much the inquirer
knew upon the subject, or the exact point at which his ignorance
commenced, a process not very agreeable to the vanity of mankind; taking
up the subject at this point, he would then very clearly and shortly
explain it.

His acquaintance with mathematics was very limited. Many years since,
when I was an unsuccessful candidate for a professorship of mathematics,
I applied to Dr. W. for a recommendation; he declined it, on the ground
of its not being his pursuit. I told him I asked it, because I thought
it would have weight, to which he replied, that it ought to have none
whatever. There is no doubt his view was the just one. Yet such is the
state of ignorance which exists on these subjects, that I have several
times heard him mentioned as one of the greatest mathematicians of the
age. [This of course could only have happened in England.] But in this
as in all other points, the precision with which he comprehended
and retained all he had ever learned, especially of the elementary
applications of mathematics to physics, was such, that he possessed
greater command over those subjects than many of far more extensive
knowledge.

In associating with Wollaston, you perceived that the predominant
principle was to avoid error; in the society of Davy, you saw that it
was the desire to see and make known truth. Wollaston never could have
been a poet; Davy might have been a great one.

A question which I put, successively, to each of these distinguished
philosophers, will show how very differently a subject may be viewed by
minds even of the highest order.

About the time Mr. Perkins was making his experiments on the compression
of water, I was much struck with the mechanical means he had brought to
bear on the subject, and was speculating on other applications of it,
which I will presently mention.

Meeting Dr. Wollaston one morning in the shop of a bookseller, I
proposed this question: If two volumes of hydrogen and one of oxygen are
mixed together in a vessel, and if by mechanical pressure they can be so
condensed as to become of the same specific gravity as water, will the
gases under these