Naturae Mag t c k. Doo^ 17,

By a Cencave-Glass to fee in the night what ii done asar off.

By this very Gliss, we may in a tempestuous night, in the middle of the streets, castthe light a great way , even into other mens Chambers* Take the Glass in yourhand, and set a Candle to the point of Inverlion , lor the parallel beams will be re-flected to the place desired, and the place will be en light ned above sisty paces, andwhatsoever falls between the parallels, will be clearly seen; the reason is, because thebeams fiom the Centre to the circumference, are reflected parallel, when the parallelscome to a point ; and in the place thus illuminated , letters may be read, and allthings done conveniently, that require great light. By the fame Art we may

With a few small lights give light to a great Hall.

In Temples, Watches, and nightly Fealis, any man any thus with a few lights makea great light. At two cr more places of the Chamber set Concave-glasses above,and let them be so ordered , than the place of concurrent parallels may be coinci-dent in the place required ; and in the point cf Inversion of them, the light will beso multiplied, that it will be as light as noon*d,ty. Lamps are best for this purpose,because the light varies not from the place. Candles are naught because they alterthe places of reflection. More ccrr.tnodieufly then by a plain Glass , to signifie by aConcave*glalj,secretly feme notes to your friend: Thus, do a? Tsaid, make the marl*upon your Glass superficies, wish wax or some dark substance , and setting it againstthe light, it will cast tbe.ligbt upon the waist of the Chamber, and there it will bedark where the letters are made : one that knows the craft > majt4isily.read them.But this is more admirable for one that knows not the,cause, -e* -

To read letters in a darkjught.

A Conca ve-Glass is of great use for this, and it may be this mav be. good in time ofneedsitv. Set your Cencave-Glass against the Stars of the first magnitude, ora-gainii or Mercury , or against a fire or light that is afar Oik; for the light re-flected will meet in the point of burning, and reflects a most bright light» wherebyyou may easily read the smallest letters ; for putting the point of reflection to everyword, you shall see all clearly. But this is more neceflary and profitable,

At any hour of the day with a Concave-Gl ■'to set a House or Fort onfire.

You may lo burn the enemies Ships, Gates, Bridges, and the like, without danger orsuspicion, at a set hour of theoay, appointed the day before. Set your Glass a-

gaiost the Sun, and order itso, that the coincidence of the beams:may.fall upon thepoint: Lay fuel there , and things that will take fire, as I shewed you: and if youwould blow up Towers, make heaps of Gun-powder: at night set your Glass, andhide it, that it be noc seen, for the next day the Sun will fall upon the same point,where you set fuel for the fire.

Chap. V.

Of themixt operations of the plain Cencave-Glaffes.

( Shall sec down the mixe operations and benefits of both these GUffes, that whatone cannot do alone, it may do by the help of another. If we would

Kindle fire afar off with a plain and a Concave Glass,

It falls cut sometimes that one shut up in prison needs fire, and the Sun beams shinenot in: or else I will stuw how we may kindle Gun-powder without fire, or makemines and fi;I them with Gun powder, ro blew up Castle- or Rocks afar off withoutdanger , setting them on fire by a plain Glass. A plain Glass as it receives the pa-rallel beams of the Sun, it lo reflects them, and therefore will cast the teams that areequidistant,* .great way ; but if a Concave-Glafs receive them, it so unites, theory kbitit sets things on fire. Wherefore, first proving where the CoLoat e^Gials ifiust be