Nature is so ample and vast, and these principles are so simple and generall, that I can observe almost no particular Effect, but that I presently know it might be deduced from thence in many severall ways: and that commonly my greatest difficulty is to finde in which of these ways it depends thereon; for I know no other expedient for that, but again to seek some experiments, which may be such, that their event may not be the same, if it be in one of those ways which is to be exprest, as if it were in another. In fine, I am gotten so far, That (me thinks) I see well enough what course we ought to hold to make the most part of those experiments which may tend to this effect. But I also see they are such, and of so great a number, that neither my hands nor my estate (though I had a thousand times more then I have) could ever suffice for all. So that according as I shall hereafter have conveniency to make more or fewer of them, I shall also advance more or lesse in the knowledge of Nature, which I hop'd I should make known by the Treatise which I had written; and therein so clearly shew the benefit which the Publick may receive thereby, that I should oblige all those in general who desire the good of Mankinde; that is to say, all those who are indeed vertuous, (and not so seemingly, or by opinion only) aswell to communicate such experiments as they have already made, as to help me in the enquiry of those which are to be made. But since that time, other reasons have made me alter my opinion, and think that I truly ought to continue to write of all those things which I judg'd of any importance, according as I should discover the truth of them, and take the same care, as if I were to print them; as well that I might have so much the more occasion throughly to examine them; as without doubt, we always look more narrowly to what we offer to the publick view, then to what we compose onely for our own use: and oftentimes the same things which seemed true to me when I first conceived them, appear'd afterwards false to me, when I was committing them to paper: as also that I might lose no occasion of benefiting the Publick, if I were able, and that if my Writings were of any value, those to whose hands they should come after my death, might to make what use of them they think fit.