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confin'd way content ones self to deliver such Experiments and Observations of the Production, or the Destruction or Change of this or that Quality, as, being duly reason'd on, may suffice to shew wherein the nature of that Quality doth consist, especially in opposition to those erroneous conceits that have been entertained about it. Of the First of these three ways of treating of a Quality I pretend not to have given any compleat example; but you will find, that I have begun such Histories in my Specimens about Fluidity and Firmness, and in the Experiments, Observations, &c. that I have put together about Cold. The Second sort of Historical Writings I have given an Instance of in my Experiments about Colours; but in these ensuing Notes, the occasion I had to make them having obliged me chiefly to have an eye to the disproval of the errours of the Peripateticks and the Chymists about them, I hope I shall not be thought to have fallen very short in my Attempt, if I have (here and there) perform'd what may be required in the Third way of writing Historically of a Quality; my present Design being chiefly to give an Intelligent and Historical Account of the Possible Mechanical Origination, not of the variousPhæ-
