return to the plainness and soundness of _Observations_ on _material_ and
_obvious_ things. It is said of great Empires, That _the best way to
preserve them from decay, is to bring them back to the first Principles,
and Arts, on which they did begin_. The same is undoubtedly true in
Philosophy, that by wandring far away into _invisible Notions_, has almost
quite destroy'd it self, and it can never be recovered, or continued, but
by returning into the same _sensible paths_, in which it did at first
proceed.

If therefore the Reader expects from me any infallible Deductions, or
certainty of _Axioms_, I am to say for my self, that those stronger Works
of Wit and Imagination are above my weak Abilities; or if they had not been
so, I would not have made use of them in this present Subject before me:
Whenever he finds that I have ventur'd at any small Conjectures, at the
causes of the things that I have observed, I beseech him to look, upon them
only as _doubtful Problems_, and _uncertain ghesses_, and not as
unquestionable Conclusions, or matters of unconfutable Science; I have
produced nothing here, with intent to bind his understanding to an
_implicit_ consent; I am so far from that, that I desire him, not
absolutely to rely upon these Observations of my eyes, if he finds them
contradicted by the future Ocular Experiments of other and impartial
Discoverers.

As for my part, I have obtained my end, if these my small Labours shall be
thought fit to take up some place in the large stock, of _natural
Observations_, which so many hands are busie in providing. If I have
contributed the _meanest foundations_ whereon others may raise nobler
_Superstructures_, I am abundantly satisfied; and all my ambition is, that
I may serve to the great Philosophers of this Age, as the makers and the
grinders of my Glasses did to me; that I may prepare and furnish them with