importance of accuracy with regard to numerical relations, and to my own
distrust of the care and correctness of translators. In the few cases where
I have extracted short passages from the works of my friends, I have
indicated them by marks of quotation; and, in imitation of the practice of
the ancients, I have invariably preferred the repetition of the same words
to any arbitrary substitution of my own paraphrases. The much-contested
question of priority of claim to a first discovery, which it is so dangerous
to treat of in a work of this uncontroversial kind, has rarely been touched
upon. Where I have occasionally referred to classical antiquity, and to
that happy period of transition which has rendered the sixteenth and
seventeenth centuries so celebrated, owing to the great geographical
discoveries by which the age was characterized, I have been simply led to
adopt this mode of treatment, from the desire we experience from time to
time, when considering the general views of nature, to escape from the
circle of more strictly dogmatical modern opinions, and enter the free and
fanciful domain of earlier presentiments.

It has frequently been regarded as a subject of discouraging consideration,
that while purely literary products of intellectual activity are rooted in
the depths of feeling, and interwoven with the creative force of
imagination, all works treating of empirical knowledge, and of the
connection of natural phenomena and physical laws, are subject to the most
marked modifications of form in the lapse of short periods of time, both
p 12
by the improvement in the instruments used, and by the consequent expansion
of the field of view opened to rational observation, and that those
scientific works which have, to use a common expression, become 'antiquated'
by the acquisition of new funds of knowledge, are thus continually being
consigned to oblivion as unreadable. However discouraging such a prospect
must be, no one who is animated by a genuine love of nature, and by a sense