Section 82

That the Image of a ConcAve-Glafs (houldgo out far from the Centre ; when y^u have obtained the Image of the thing in its point, if you will have it farther di!taiu fr-m the Centre,and that the Picture of a thing fhall be farther ftrctched forth, then voufha:l decline frcm the point a little toward the right cr left hand, about the 'upr-rhcic of the Glafs, and the Image will come forth the farther , and will come to your fi^ht : There, nimely where the Catheins doth the fartheft eff that is poflible r ouch in.- hne of reflection , which few have obferved :from which principle jmny (irangc wonders may be done. When you have this, you may eafily
T^efieEl heat, calJ, and the voice too, by aConcave-GUfs .
If a man put a Candle in a place, where the vifible Object is to be fet , the Candle will come to your very eyes , and will offend them wi.h its heat and light. But this is more wonderful , that as heat , fo cold , fhould be refle&ed : if you put fnow in that place , if it a me to the eye , becaufe it is fenfible, it will presently feel the cold. But there is a greater wonder yet in it j for it will not onely reverberate heat and cold , but the voice too, and make an Eccho ; for the voice is more rightly re- flected by a polite and imooth fuperficies of the Glafc, and more compieatly than by any wall. I prove this, becaufe, if a man turn his face to the Glafs , and his friend ftand far behind his back, when he beholds his face, he fhall decline his face from the point of Invcrfion ; but on the right hand, about the fuperficies of the Glafs , and his face will come forth far from the Glafs , and will feem very great abouc thefacc of his friend : Whatfoever he fhall fpeak with a low voyce againlt the Glafs, he fhall hear the fame words and motions of his mouth , and all motion from the mouth of the reflected Image; and they that ftand in the middle between them, fhall per- ceive nothing at all. But he that would fend his own Image to his friend, mult ob- fcrve till his head (hall come to the Glafs. It is profitable alfo
Ccc B;
6% Nat u-r a l M agio k. 2>00^ 17.
By a Concave*Glafs to fee in the night what is done afar off. By this very Glafs, we may in a tempeftuous night, in the middle of the fireets , ctft the light agreat way, even into other mens Chambers. Take the Glais in your hand, and let a Candle to the point cf Inverfion , tor the parallel beams will be re- flected to the place defired, and the place will be enlightned above fmy paces, and whatfoever falls between the parallels, will be clearly feen : the reafon is, becaufe the beams fiom the Centre to the circumference, are reflected parallel, when the parallels come to a point ; and in the place thus illuminared, letters may be read, and all things done conveniently, that require great light. By the fame A rt we may
With a few [mall lights give h^htto a great Hall. In Temples, Watches, and nightly Featts , any man m?y thus with a few lights make a great light. At two or more places of the Chamber fet Concave-gkffes above, and let them befo ordered, that the place of concurrent parallels may be coinci- dent in the place required ; and in the point of lnvtrfionof them, the light will be fo multiplied, that it will be as light as noon-day. Lamps are beft for this purpofe, becaufe the light varies not from the place. Candles are naught , becaufe they alter the peaces of reflection. More commodieufly then by a plain Glafs , to fignifie by a Concave-glals,fectetly feme notes to your friend: Thus, do a? I faid, make tr.e marks upon your Glais fuperficies with wax or fome dark fubftance , and fetting it againft thr light, it will cart the light upon the walls of the Chamber, and there it will be dark where the letters are made : one that knows the craft, may eafily read them. But this is more admirable for one that knows not the caufe,
To read letter sin a darkjiight. A Corsave-Glafs is of great ufe for this, and it may be this may be good in time of r.ectfluv. Set your Ccncave-Glafs againti the Stars of the firft magnitude, or a- gainM Ver.tu or Mercury , or a.:ainft a fire or light that is afar tfff; 'for the light re- flected will meet in the point of burning, and reflects a moft bright light , whereby youmayeafiiy read the fmalleft letters ; for putting the point of reflection to every word, you (hall lee all clearly. But this is more necefiary and profitable,
At any hour of the daj with a Concave-Ghjs, to fet a Houfe or Fort on fire. ^ oa may fo burn the enemies Ships, Gates, Bridges, and the like, without danger or fulpicicn, at a fee hour of the day, appointed the day before. Set your Glafs a- gainfttheSun, 'andf rderitfo, that (he coincidence of the beams may fall upon the point: tayfud there, and things that will take fire, as I (hewed you: and if you would blow up Towers, make heaps of Gun-powder: at night fee your Glafs, and' hide it, that it be not feen, for the next day the Sun will fall upon the fame point, where you fet fuel fcr the fire.
Chap. V.
Of themixt operations of the flam Concave- Glaffes.
(Shall fet down the mixt operations and benefits of both thefe Glaffes , that what one cannot do alone, it may do by the help of another. If we would
Kindle fire afar off with a plain and a Concave Glafs. It falls rut fometimes that ere fbut up in prifon needs fire, and the Sun beams fbine not in : orelfeT will fliew how we may kindle Gun-powder without fire , or make mines and fill thcm with Gun-powder, to blow upCaftles or Rocks afar off without danger , Jetting them on fire by a plain Glafs. A plain Glais as ir receives the pa- rallel beams of the Sun, it fo reflects them, and therefore will caft the beams that are equidirtant,a crcat way : hut if a Concavc-Glafs receive them, it i'o unites them, that it fees things on fire. Wherefore, firft proving where the Concave- Glafs muft be
©laced
Of jlrange Cjlajfes. y&\
placed,thatitmayfirethefuclca iin : the next day, at the hour appointed, let ihe piain Glafs caft in the bcarm upon the Concave- glafs,t hat will unite them : To with- out danger, or any i'ufpicicnof the enemy, we may kindle fire for our life, Nor is it
ufeiefs, v v
That by a plain and (foncave-Glafs the fmallejt letters {ball ^ppexr very great,
when letters are fo fmall that they can ©nely be fcen : For I have feen St Johns Go- fpel, /» the be;tf.ning)iic. writ fo fmall, in fo little place , that it was no bigger than a fmall pimple, or me fight in a Cocks eye. By this Artifice we may mske them feem greater , and read them with eafc. Put a Concave-glafs, with the back ot it to yourbreft; over againft it in the point of burning, fct the writing: behind let a plain Glafs, that you may fee it : Then in the plain Glafs will the Images of the Cha- rters be reflected , that are in the Concave-gia fs, which the Concave-Glafs hath trade greater, that you may read them without difficulty. You may
With a flam and Concave-Glafs, make an Image be feen hanging altogether in the Air.
Do thu>. I faidtbar by help of a Concave-Glafs, an Image may be fent forth : an^ this i: feen by none but thoic that ftand over againft it ; Set the Concave-Glafs to yourbreft, without the Centre place a Poniard againft it, and going farther off, fee a plain Glafs againft it ; and looking in that , you fhall fee the Image reflected trcrn the Concave- glafs, hanging in the Air, and that exactly. But if an ingenious man obferve it, he may wonderfully fee an Image hanging in the Air, that is received in aplainG^als, and fent far out as I fhewed, without the help of a Concave-glafs, and a vifible ipc&acle , by the means of a plain Glafs cnely, You may alfo
By a ylain Gfafs fee yomface turned the wrong way. When you have fet the Glafs to your breft, as I faid ; fet a plain Glafs againft ir, and look upon it , it will caft it upon the Concave-glafs , and that will beat it backwards on the plain Glafs : fo have you your purpofc.
Chap. VI.
Other operations of a (foncave-Glafs.
BE ore I part from the operations of this Glaf?, I will tell youfome ufeof ir,that u very pleafant and admirable, whence great fecrets of Nature may appear unto uj. As,
To fee all things m the dark^ that are outwardly done in the Sm^with ihe colours of them.
You muft iTiU' all the Chamber windows , and it will do well to fhut up all holes be- fides, left any ltghc breaking in fhcu!d fooil all. Onely make one hole, that fhall be a bands breadth ir, fo thick as a pa p^r. open a round hole in the middle or it , as great as your little finger : over againft this, let there be white w alls of paper, or white clothes, fo fhall yon fee all that is done without in the Sun , and thofe that walk in the ftreets, like to Antipodes, and what is right will be the left, and all things changed • and the far- ther they are eff from the hole, t he greater they will appear. If yen bring your pi- per, or white Table neerersthey wiliftiew lefs and clearer; butycumulf ftay awhile, for the Images will not be feen pre le nt ly : becaufe a ftrong fimilitude doth feme- times make a great fenfation with the fence , and brings in Inch an iffecsion, that not onely when the fenfes do a&, are they in the organs, and do troOvle them, but when they hive done acting, they will ftay long in them: which may e'afiiy be perceived. For when men walk in the Sun , if they come tni o the dark, that affection continue.*-, thar we can fee nothing, cr very fcantly ; becaufe the affection made by the tight , is fi'l in cur eyes ; and when that is gone by cegrecs, we fee clearly in dark places. Now will I declare what I ever concealed till row , ard thought to conceal com ibu» *Uy. It you pnt a fmali ecmicular Cryftal glafs to the hole , you (hall prefently fee
C c c 2 ail
}
all things clearer , the countenances of men walking, the colours, Garments , and *H things as if you flood hard by ; you fhall fee thern with fo much pieafure , that thofe that fee it can never enough admire it. But if you will
See all things greater and clearer,
Over againft it fet the Glafs , not that which difF pates by difperfing , but which con- gregates by uniting, both by coming to it, and going from it , till you know the true quantity of the Image , by a due appropinquation of the Centre ; and fo (hall the be- holder fee more fitly Birds flying, the cloudy skies , or clear and blew, Mountains that are afar off ; and in a fmall circle of paper (that is put over the hole) you {hall fee as it were an Epitomy of the whole world , and you will much rejoyce to fee it : all things backwards, becaufe they are neer to the Centre of theGlais,if you fee them farther from the Centre , they will fhew greater and upright, as they arc, but not fo clear. Hence you may,
Ifyou cannot draw a Pittttre of a man or any things elfe, draw it by this means •
If you can but onely make the colours. This is an Art worth learning. Let the Sun beat upon the window, and there about the hole, let thercbe Pictures of men, that it may light upon them, but not upon the hole. Put a white paper againft the hole , and you fhall fo long fit the men by the light , bringing them neer, or fetting them further,until the Sun cart a perfeft reprefentation upon the Table againft it tone that is skill'd in painting, muft lay on colours where they arein the Table, and (hall defcribe the manner of the countenance ; fo thelmage being removed , the Pi&ure will remain on the Table, and in the fuperficies it will be fcen as anjmage in a Glafs. Ifyou will
That all fhall appear right9
This is a great fecret : many have tryed it, but none could obtain it : For feme fetting Plain Glaffes obliquely againft the hole, by reverberation againft the Table, they could feefome things fomewhat direct , but dark and not difcernable. I oft-times by putiing a white paper obliquely againft the hole, and looking juft againft the hole, could fee fome things direct : but a Pyramis cut obliquely, did (hew men with- out proportion , and very darkly. Bur thus you may obtain your defire : Put a- gainft the- hole a convex Glafs ; from thence let the Image reflect on a Concave- glafs: let the Concave-glafs be diftant from the Centre, for it will make thofe I- mages right, that it receives turned , by reafon of the diftance of the Centre. So up- on the hole and the white paper, it will caft the Images of the Objects fo clearly and plainly , that you will not wonder a little. But this I thought fit to let you under- stand , left you fail in the work, that the Convex and Concave- glsffes be proporti- onable circles: how you fhall do this, will be here declared often. I fhall (hew alfo,
How in a (Chamber you may fee Hunting, Battles of Sr.emics, and other delft fons.
Now for a condufion I will add that , then which nothing can be more pleafant for great men, and Scholars, and ingenious perfons to behold ; That in a dark Chamber by white flieets objected , one may fee as clearly and pcrfpicooufly , as if they were before his eyes, Huntings, Banquets, Armies of Enemies, PJays , and all things elfe that one defireth. Let there be over againft that Chamber, where vou defire to reprefent thefe things, fomefpacious Plain, where the Sun can freely fhine: Upon that you fhail fet Trees in Order , alfo Woods, Mountains, Rivers, ard Animals, that are really fo, or made by Art, o Wood, or feme other matter. Ycumuft frame little children in them, as we ufe to briog them in when Comedies are A#ed : and you muft counterfeit Stag', Bores, Rhinocerets, Elephants, Lions, and what other creatures you pleafc : Then by degrees they muft appear, as coming out of their dens, upon the Plain : The Hunter he muft come with his hunting Pole, Nets, Arrows, and other neceflaries , that mav reprefent hunting: Let there be Horn?, Cornets, Trum Decs founded : thofe that are in the Chamber fliall fee Trees, Animals, Hun- ters Faces , and all the reft fe plainly , that they cannot tell whether they be true
or
Of Jlrange Cjlajfes. ^6^
or delations: Swords drawn will glift r in atihet.cle, that they will m?k^ people almoft afnid. I have often (hewed this kind of Spectacle to my friends, wi.o much admired it, and tookpieafure to fee ftich a deceit ; and I could hardly by naturaj rcafons, and reafons from the Opticks remove them frcm their opinion , when I \ -} dtfecvered the fecret. Hence ic may appear to Philolopher?, and thofc that \-.wi-; Opti k?, howvifion is made; and thequei ionof intrcmitfion is taken away , that was antiently fo v i!cu(ted;nor can there be any better way to demon! rate hot fy nan this. The Image is let in by the pupil, as by the hole of a window ; and t hat part of the Sphere, that is ret in the middle of the eye, (lands in flead of a I know ingenious people will be much delighted in this. It is declared more at large in our Opticks. From hence may one take his principles of declaring any thing to one that is confederate with him, that is fecret, though the party be far off, (hut up in prifon. And no fmall Arts may be found out. You (hall amend the diliance by the magnitude of the Glafs. You have fufficienr. Others that undertook to teach this, have utter*d nothing but toyes, and 1 think none before knew it. If you defire to know
How yon may fee the Sun Eclipfed,
Now T have determined to (hew how the Suns Eclipfe may be feen.When the Sun is Eclipfed, {hut your Chamber- windows, and put a paper before a hole, and you (hall fee the Sun : let it fall upon the paper oppofite from a Concave-glafs ^ and make a circle of the fame magnitude: do fo at the beginning, middle, and end of ir. Thus may you without any hurt to your eyes, obferve the points of the diameter of the Suns Eclipfe,