New experiments physico-mechanical, touching the air
Boyle, Robert, 1627-1691., Sharrock, Robert, 1630-1684., Boyle, Robert, 1627-1691. Defence of the doctrine touching the spring and weight of the air., Boyle, Robert, 1627-1691. Examen of Mr. T. Hobbes his Dialogus physicus de naturâ aëris.
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To the Reader.

ALthough the following Treatise being far more prolix than becomes a Letter, and than I at first intended it; I am very unwilling to encrease the already excessive bulk of the Book by a Preface, yet there are some Particulars that I think my self oblig'd to take notice of to the Reader, as things that will either concern him to know, or me to have known.

In the first place then: If it be demanded why I publish to the World a Letter, which by its Style and diverse Passages, appears to have been written as well For, as To a particular Person; I have chiefly these two things to answer: The one, That the Experiments therein related, having been many of them try'd in the presence of Ingenious Men; and by that means having made some noise among the Virtuosi (insomuch that some of them have been sent into Foreign Countries, where they have had the luck not to be des∣pis'd) I could not, without quite tyring more than one Amanu∣ensis, give out half as many Copies of them as were so earnestly desired, that I could not civilly refuse them. The other, That intelligent Persons in matters of this kind, perswade me, that the publication of what I had observ'd touching the nature of the Air, would not be useless to the World; and that in an Age so taken with Novelties as is ours, these new Experiments would be grate∣full to the Lovers of free and real Learning: So that I might at once comply with my grand Design of promoting Experimental and Usefull Philosophy, and obtain the great satisfaction of giving some to ingenious Men; the hope of which, is, I confess, a temp∣tation that I cannot easily resist.

Of my being somewhat prolix in many of my Experiments, I have these Reasons to render, That some of them being altogether new, seem'd to need the being circumstantially related, to keep the Reader from distrusting them: That divers Circumstances I did Page  [unnumbered] here and there set down for fear of forgetting them, when I may hereafter have occasion to make use of them in my other Writings: That in divers cases I thought it necessary to deliver things cir∣cumstantially, that the Person I addressed them to might, with∣out mistake, and with as little trouble as is possible, be able to re∣peat such unusual Experiments: and that after I consented to let my Observations be made publick, the most ordinary reason of my prolixity was, That foreseeing that such a trouble as I met with in making those trials carefully, and the great expence of time that they necessarily require (not to mention the charges of making the Engine, and imploying a Man to manage it) will probably keep most Men from trying again these Experiments: I thought I might do the generality of my Readers no unacceptable piece of service, by so punctually relating what I carefully observ'd, that they may look upon these Narratives as standing Records in our new Pneu∣maticks, and need not reiterate themselves an Experiment to have as distinct an Idea of it, as may suffice them to ground their Reflexions and Speculations upon.

And because sometimes '-tis the Discourse made upon the Experi∣ment that makes it appear prolix, I have commonly left a conspicu∣ous interval betwixt such Discourses, and the Experiments where∣unto they belong, or are annexed; that they who desire only the Historical part of the account we give of our Engine, may reade the Narratives, without being put to the trouble of reading the Reflexions too: which I here take notice of for the sake of those that are well vers'd in the New Philosophy, and in the Mathema∣ticks; that such may skip what was design'd but for such Persons as may be less acquainted, even than I, with matters of this na∣ture (scarce so much as mentioned by any Writer in our Lan∣guage) and not for them from whom I shall be much more forward to learn, than to pretend to teach them. Of my being wont to speak rather doubtfully, or hesitantly, than resolvedly, concerning matters wherein I apprehend some difficulty, I have in another Treatise (which may, through God's assistance, come abroad ere long) given a particular, and, I have, a satisfactory account: wherefore I shall now defend my practice but by the Observation of Page  [unnumbered]Aristotle, who somewhere notes, That to seem to know all things certainly, and to speak positively of them, is a trick of bold and young Fellows: whereas those that are indeed intelligent and con∣siderate, are wont to imploy more wary and diffident expressions, or (as he speaks) 〈 in non-Latin alphabet 〉.

There are divers Reflexions, and other Passages in the following Epistle, and even some Experiments (occasionally mention'd) which may seem either impertinent or superfluous, but are not so: Being purposely written, either to evince some truth oppos'd, or disprove some erroneous conceit maintain'd by some eminent New Philosopher, or by some other Ingenious Men, who, I presum'd, would easily forgive me the having on such occasions purposely omit∣ted their Names; though an inquisitive Person will probably dis∣cover divers of them, by the mention of the Opinions disprov'd in the Experiments I am excusing.

Ever since I discern'd the usefulness of speculative Geometry to Natural Philosophy, the unhappy Distempers of my Eyes, have so far kept me from being much conversant in it, that I fear I shall need the pardon of my Mathematical Readers, for some Passages, which, if I had been deeply skill'd in Geometry, I should have treated more accurately.

And indeed, having, for Reasons elsewhere deduc'd, purposely kept my self a stranger to most of the new Hypotheses in Philoso∣phy, I am sensible enough that the Engine I treat of hath prevail'd with me to write of some subjects which are sufficiently remote from those I have been most conversant in. And having been reduc'd to write the greatest part of the ensuing Letter at a distance, not only from my Library, but from my own Manuscripts, I cannot but fear that my Discourses do not only want many choice things wherewith the Learned Writings of others might have enriched or imbelished them: But that partly for this reason, and partly for that touch'd upon a little before, It is possible I may have mention'd some No∣tions already publish'd by others, without taking notice of the Au∣thors, not out of any design to defraud deserving Men, but for want of knowing such particulars to have been already publish'd by them: Especially the Experiments of our Engine being themselves suffici∣ent to hint such Notions as we build upon them.

Page  [unnumbered]The order of the Experiments every Reader may alter, as suits best with his own design in perusing them: For not only all those betwixt whom there is an Affinity in Nature (by belonging to one subject) are not always plac'd one by another, but they are not still set down so much as in the order wherein they were made; but most commonly in that casual one wherein my occasions induc'd me to dispatch them to the Press. And, which is worse, I did usually send quite away the former Experiments, before the later were written, or perhaps so much as made: Whereby I lost the advantage of cor∣recting and supplying the Imperfections of what I had formerly written, by the light of my subsequent Trials and Discoveries.

Besides all this, the distemper in my Eyes forbidding me not only to write my self so much as one Experiment, but even to reade over my self what I dictated to others: I cannot but fear, that besides the Author's mistakes, this Edition may be blemish'd by many, that may be properly imputed to a very unskilfull Writer (whom I was often∣times by haste, reduc'd against my custome, to imploy) and may have escaped the Diligence of that Learned Friend, that doth me the favour to oversee the Press; especially, there being the distance of two days Journey betwixt it and me.

I need not, perhaps, represent to the equitable Reader, how much the strange Confusions of this unhappy Nation, in the midst of which I have made and written these Experiments, are apt to disturb that calmness of mind, and undistractedness of Thoughts, that are wont to be requisite to Happy Speculations. But I presume, that by all these things put together, he will readily perceive, That I have been so far from following the Poet's prudent Counsel touching the flow Publication of Books design'd to purchase credit by,

—Nonumque prematur in Annum
that I suffer this Treatise to come abroad into the World with a mul∣titude of disadvantages.

But if it be demanded, why then I did not make it fitter for the Press before I sent it thither? my Answer must be, That not at first imagining that this sort of Experiments would prove any thing Page  [unnumbered] near so troublesome, either to make, or to record, as I afterwards found them, I did, to engage the Printer to dispatch, promise him to send him the whole Epistle in a very short time: So that al∣though now and then the occasional vacations of the Press, by rea∣son of Festivals, or the absence of the Corrector, gave me the leisure to exspatiate upon some subject; yet being oftentimes call'd upon to dispatch the Papers to the Press, my promise, and many unexpected Avocations, obliged me to a haste, which, though it hath detracted nothing from the Faithfulness of the Histerical part of our Book, hath (I fear) been disadvantageous enough to all the rest. And I made the less scruple to let the following Pa∣pers pass out of my hands, with all their Imperfections; because, as the Publick Affairs, and my own, were then circumstanc'd, I knew not when, (if at all) I should be again in a condition to prosecute Experiments of this kind; especially, since (to omit my being almost weary of being, as it were, confin'd to one sort of Experi∣ments) I am pre-ingag'd (if it please God to vouchsafe me Life and Health) to imploy my first leisure in the publication of some other Physiological Papers, which I thought'twould make me much the fitter to take in hand, if I first dispatch'd all that I had at this time to write touching our Engine.

I have this farther to add, by way of Excuse, That as it hath been my design in publishing these Experiments to gratifie Ingenious Men; so, if I have not been much flattered, I may hope that the various hints to be met with in the following Letter, will (at least) some∣what awaken Mens thoughts, and excite them to new Speculations (such as perhaps even inquisitive Men would scarce else light upon) and I need not despair, that even the examination of such new Suspicions and Enquiries will hence also, at least occasionally, be fa∣cilitated: I said occasionally, because it being, as'tis proverbially said, Facile Inventis addere: It seems not irrational to expect, that our Engine it self, and divers of our Experiments, will be much promoted by the industry of Inventive and Mathematical Wits, whose Contrivances may easily either correct or supply, and conse∣quently surpass many of those we have made use of. And, particu∣larly, if Men by skill and patience can arrive both to evacuate such Page  [unnumbered] Receivers as ours, till there be no more Air left in them, than there seems to have remain'd in the Glasses made use of about the Mag∣deburgick Experiment (hereafter to be mentioned) and to keep out the Air for a competent while, the Usefulness and Discoveries of our Engine, will not be a little advanc'd. And perhaps that may belong to it, which I remember Seneca speaks of Nature: Initiatos (saith he) nos credimus, in Vestibulo ejus haeremus: For being now in a place where we are not quite destitute of moderately skil∣full Artificers, we have since the Conclusion of the following Let∣ter, made some Additions to our Engine, by whose help we find (upon some new trials) that we may be able, without much of new trouble, to keep the ambient Air out of the exhausted Receiver for a whole day; and perhaps we should be able to keep it out much longer, if before we shall have dispatch'd some urgent Affairs, and publish'd some Papers for which a kind of Promise is thought to make us Debtors to the Press, we could be at leisure to prosecute such Experiments, as may possibly afford a Supplement to the fol∣lowing Treatise, from which I shall now no longer detain the Reader.