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 0