holds. We desire, therefore, you would at your leysure instruct us farther in the demonstrations of all the cases remayning, which I suppose you can easily and soone doe out of the severall figures in the English paper. We long to heare fro you and to receive those things you promis'd. My Lord would gladly be a partaker of, and a student in your philosophicall discourses, if you would impart them to him. He is much taken with the device of your perspective glasse and desires you would calculate a line for it, at a good proportion, as 40 to one, that we might see whether it would hold good in practise as well as it seems in speculation; and if it doe, he will be ready to further you in any way you shall desire. Both his Lordship and Sir Charles recommend their love to you and soe does Your friend to serve you, Rob ERT PAYN E. SIR CHARLES CAVENDISH TO WALTER [MS. Birch, Brit. Mus. 4405, fol. 161, Orig.] Worthie Sir, Though I have had some diversions, yet I aske your pardon that I have bin so longe before I returned you thankes for the two tracts you were pleased to send me; I give you manie thankes for them, and esteem (as they justlie deserve) verie greatlie of them. I received latelie a letter from Mr. Hobbes, where amongst other things he sent me this paper heer inclosed, which is an experiment of the place of the image of a thing contrarie to the olde tenet; a candle being put into a glasse of a cylindricall forme, the image hangs perpendicularlie over the candle itself, as is expressed in this figure, and not at the concourse of the perpendicular from the object with the visuall line which in this figure is at the point A. Mr. Hobbs conjectures that the approach of the image proceeds from the strength of action from the object, which is greater heere than in a plaine, by reason of the concavitie of the cylinder which gathers the beames, and by that meanes makes the motion or streame of the reflected beames stronger. I desire at your convenient leasure to have your opinion of it, as also of this place of the image in convex glasses. I have sent you by this bearer, Mr. Butler, twentie pounds as our acknowledgment of your favoure. And so wishing you all hapiness, I remaine Your assured freind, CHARLEs CAVENDYssh E. SIR CHARLES CAVENDISH TO WALTER [MS. Birch, Brit. Mus. 4444, fol. 91. Orig.] Worthie Sir, I give you many thankes for the two tracts you sent me, one of the place of the image in concave and convex glasses, and the other of the making of prospective glasses. I will not trouble you with a repetition of some doutes which Mr. Payen and I have of some things in these tracts, but refer you to his letter, for he hath promised me to write to you of them. The greatest doute that I have in your tract of the place of the image is howe the eye can take notice of the laterall beames which are without the eye, for sight being made, as you write, upon the retiform tunicle, I conceive not howe we can take notice of the laterall beams which are refracted before they come thither, or, as I conceive, we take no notice of that refraction. Sir, you see the boldness I take to trouble you, which your former favours have encouraged me to doe. And so wisshing you all hapiness, I rest, Your assured freind, ROBERT PAYNE TO WALTER WARNER. [MS. Birch, Brit. Mus. 4458, fol. 26. Orig.] Good Mr. Warner, Though the plague (thanks be to God) hath not yet come mere us, yett we feele the ill effects of it. One whereof is, the interruption of intercourse of letters fro” us to you, and you to us. I had some time since written to you concerning the two tracts you sent last to Sir Charles Cavendysshe, but I was not certaine where you were, or how my letter should come at you. Now having notice of your continuance at Cranborne lodge, and the conveniency of a passenger that way, I have advertised these lines to you, desiring to heare from you agayne by the next opportunity you can finde. In your tract De Loco Imaginis, &c., the theoremes you take for principles, undemonstrated, require demonstration, as much as the conclusion you would proove by them, which yourself having first given notice of, I suppose it worth your paines to send their demonstrations: and so to cleere the manner of vision, how it is made, demonstratively; for as yet we take all upon probability. But suppose these theoremes were demonstrated, there is yet one maine doubt remaining; and that is, how the sense should take notice of the laterall beames, which only touch on the superficies of the eye, and enter not into it directly, but refracted. And if the sense follow the direction of the refracted beame, that leads it not to the object. As suppose the lateral beame be * r BO; the refracted beame in the eye O'A; o the doubt is, how the sense can take notice of B O without the eye, soe as by that o to be descried in the place of the image. _- || | T ~ Whereas it seemes more probable the eye should be sensible only of the beame O A, which is within it; but then if it follow the direction of this beame AO, it will lead it to P, against all experience. But it may be, the cleare expression and good proofe of the manner how vision is made, will satisfye this inquisition and cleare the doubt; I meane the manner how simple vision is made, and how in that the sense judges the object without it to be in such a place, and not short or further on ; for though this forme is a thing evident of itself, yet when I consider it more seriously, I finde it not sufficiently demonstrated by any I have yett read. Agayne, supposing the sight to be discovered on the lateral beames, yet it is not thoroughly apparent why it should judge the place of the object to be in the concurse of these beames. You will say perhaps, else it would judge the object to be in two places. This I well conceive as an absurdity crossing under experience; but the cause a priori is the thing I looke for and would have, if it may be had. And indeed this lawe well cleered would necessaryly conclude the former, except single vision may be made on one line, and then the former doubt must be cleered by itself. Concerning your other tract of the Prospective. The short time I stayd with you permitted me not to take sufficient in structions from you to satisfye Sir Charles in the matter of that calculation; nor the effects of the glass focus according to the measures of it. The doubts we conceive of its effects, supposing the calculations right, are these. 1. How clere vision can be made, by beames tending to an angle in the eye: for this seemes contrary to one of the theoremes undemonstrated in your other tract: but your glass drawes the beames to an angle on the eye. 2. How one beame can be sufficient to cause cleare vision of the point whence it comes; for soe your glass seemes to be calculated, to refract ordinately but one beame from one point of the object. 3. But if you say the glass so form'd will convey all the beames falling on it from one poynt ordinately to the eye, this would be well demonstrated; for else it would cause confusion, and so destroy, if not all, at least clere and distinct VISIOIl. 4. Lastly, supposing all before were made good; the question is whether the hand or toole of any artificer be able to worke the formes or moulds, and consequently the superficies of the glass soe true, as that to nature they shall be distinguished from other convexe superficies, as the spheriques, coniques, &c. Sir, I know it is a difficult taske for you to treat by letters, but since we have yet no other way, and that the infectious ayre hinders both yours and my gooing to London, where we might meet to consider how to bring this to some good pass, I desire you to doe us the favour, in the meane while, to write to us as oft as you can. I heare Mr. Hobbes is expected, with his charge, very shortly. I doubt not but he will finde you out; and by him you may send your letters to us, if you can finde no other. Or if you send your packett to one Mr. Boothe, steward to the Countess of Devonshyre, at Byflett, nere Oatlands, to be sent by him to me at Welbeck; in regard of messengers that pass between them and us, your letters will come to us that WaV. Ši, I beseech you present my humble service to the noble knight and lady, where you are, as also to Mr. Aylsbury and Mr. Hyde, with my hearty thanks to them for their favours. Soe God keepe you and Your faythfull friend and servant, . Rob ERT PAYNE. To his friend, Mr. Rouse, Fellow of Oriel College, and Keeper of the public Library in Oxford. Mr. Rouse,_Having occasion to send to Oxford, I have sent you a copy of my period for Dr. Morrison, not so fair a one as I would, (during mine imprisonment my papers of some were many of them stained, and some quite marred with wet:) but indeed all that I have left, except only that with Dr. Bainbridge his censure, and mine answer to it; a transcript whereof, and of my postcript in the bottom of my table hung in the library, being some part of it worn away, I have sent withal: that you might the better understand what I said to you, of hanging up a better in its place. I pray you remember my service to Dr. Morrison : I would I were able to gratify him or any of you all in a better matter. I pray you also, as you have fit opportunity, remember me to Dr. Turner; I was indeed very desirous to have spoken with him, and tarried all that afternoon, the night following, and the next day, till past nine oclock in Oxford, only for that cause: and when he sent me word by his man, that I could not speak with him till two oclock in the afternoon, the excuse that I made was true, that my horse was weak, and borrowed but for a day: whereunto I might have added, that the poor man of whom I borrowed him (my nephew, the bearer hereof, lately one of your college tenant’s tenant in Kenington, whose errand to Oxford at this time is to bring a child of his, one of my grand nephews, to be a chorister in New College,) hath none other means to get his living but by his teem, whereof that was one, and the principal his fliller: as all your college tenants and the whole town of Kenington can witness: and therefore I was loth to adventure the wronging of him in that kind; especially this busy time of harvest, and opportunest time of the year to cart any whither. Otherwise I could have been content to have further attended Dr. Turner's leisure. So with remembrance of my duty to my betters, and with my duty and my best service to my good nurse the University of Oxford, I remain Yours to be commanded in what I may, Allerton, Aug. 2, 1638. |