EXPERIMENTS AND CONSIDERATIONS Touching COLOURS. First occasionally Written, among some other _Essays_, to a Friend; and now suffer'd to come abroad as THE BEGINNING Of An Experimental History OF COLOURS. By the Honourable ROBERT BOYLE, Fellow of the ROYAL SOCIETY. _Non fingendum, aut excogitandum, sed inveniendum, quid Natura faciat, aut ferat._ Bacon. _LONDON._ Printed for _Henry Herringman_ at the _Anchor_ on the Lower walk of the _New Exchange._ MDCLXIV. * * * * * THE PREFACE. Having in convenient places of the following Treatise, mention'd the Motives, that induc'd me to write it, and the Scope I propos'd to my self in it; I think it superfluous to entertain the Reader now, with what he will meet with hereafter. And I should judge it needless, to trouble others, or my self, with any thing of Preface: were it not that I can scarce doubt, but this Book will fall into the hands of some Readers, who being unacquainted with the difficulty of attempts of this nature, will think itn strange that I should publish any thing about Colours, without a particular Theory of them. But I dare expect that Intelligent and Equitable Readers will consider on my behalf: That the professed Design of this Treatise is to deliver things rather _Historical_ than _Dogmatical_, and consequently if I have added divers new _speculative_ Considerations and hints, which perhaps may afford no despicable Assistance, towards the framing of a solid and comprehensive Hypothesis, I have done at least as much as I promis'd, or as the nature of my undertaking exacted. But another thing there is, which if it should be objected, I fear I should not be able so easily to answer it, and that is; That in the following treatise (especially in the Third part of it) the Experiments might have been better Marshall'd, and some of them deliver'd in fewer words. For I must confess that this Essay was written to a private Friend, and that too, by snatches, at several times, and places, and (after my manner) in loose sheets, of which I oftentimes had not all by me that I had already written, when I was writing more, so that it needs be no wonder if all the Experiments be not rang'd to the best Advantage, and if some connections and consecutions of them might easily have been mended. Especially since having carelessly laid by the loose Papers, for several years after they were written, when I came to put them together to dispatch them to the Press, I found some of those I reckon'd upon, to be very unseasonably wanting. And to make any great change in the order of the rest, was more than the Printers importunity,