le, and popular
account of the discoveries of each of those distinguished individuals,
of a kind constituting in fact a brief history of the particular branch
of science to which he was devoted. And in the selection included in the
present volume, which constitutes but a portion of the entire series, we
have comprised the accounts of men of such varied pursuits as to convey
no inadequate impression of the progress of discovery throughout a
considerable range of the whole field of the physical sciences within
the last half century.

The account given by the author, of the principal discoveries made by
the illustrious subjects of his memoirs, is in general very luminous,
but at the same time presupposes a familiarity with some parts of
science which may not really be possessed by all readers. For the sake
of a considerable class, then, we have taken occasion, wherever the use
of new technical terms or other like circumstances seemed to require it,
to introduce original notes and commentaries, sometimes of considerable
extent, by the aid of which we trust the scientific principles adverted
to in the text will be rendered easily intelligible to the general
reader.

In some few instances also we have found ourselves called upon to adopt
a more critical tone; where we were disposed to dissent from the view
taken by the author on particular questions of a controversial kind, or
when he is arguing in support, or in refutation, of opposing theories on
some points of science not yet satisfactorily cleared up.

We could have wished that our duty as translators and editors had not
extended beyond such mere occasional scientific or literary criticism.
But there unfortunately seemed to be one or two points where, in
pronouncing on the claims of distinguished individuals, or criticizing
their inventions, a doubt could not but be felt as to the perfect
_fairness_ of Arago's judgment, and in which we were constrained to
express an unfavourable opinion on the manner in which the relative
pretensions of men of the highest eminence seemed to be decided,
involving what might sometimes be fairly regarded as undue prejudice,
or possibly a feeling of personal or even national jealousy. Much as we
should deprecate the excitement of any feeling of hostility of this
kind, yet we could not, in our editorial capacity, shrink from the plain
duty of endeavouring to advocate what appeared to us right and true; and
we trust that whatever opinion may