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Mr. Gr/go'ry {peaklng of these Instruments, m the ifoTesiid Book, Pag. HZ-.saith j De Mechanica lycrrum Speculorum iS Lentium, ii b abris frisfira tentath, 'egiin Mechanicis minus versatus nihil ilko. So that thfcre havc been Ttialsmade of these Telescopes, bnt yet m vaih. And I am mformed, that abowt7 or 8 years frnee, Mr. Qregbry htmlelf, at Lomkfit, catded ohe of 6 foot to bemade by Mr. Heive, Vhich I take to have been accordtng 'to the -aferefaid De-sign delcribed in his Book ; but, thöugh made by a sktllul Artist, yet it wa*without Saccesi.

H ctti-Dtop. ' XX. 5 . Salvetti hath made a little Prospective Glafs, made accordlftg tofcj S^Salvetti.' Mr. Newton 3 new Invention. It was not above half a foot long, it had then. 87. f. ;o<;. (ame Effect of one of two. He is now rhaking änother aster the Gonceit c/fMr .Cnjfegrain, though he agrees not with him in niaking Gdnvex the littleSpeculum, which orse looks into through the Eye Glafs, but belieVes 'theFrench Author only devised that to disguile as much as was poflible his pre-tended new Invention, which he endeavours tö marke Anterior to Mr. Newtotisj raost noble one.

To*i4\t the Fi- XXI. i. Opposite to the Place or Wall, whett the Appärition is to bc,aure of any J et a pj 0 j e ma de of about a foot in Diameter, or bigger : if there be a'tigbfRooZ T 11 high Window, that hath a Ca(ement in it, ’twill be lb much the bettethj Dr. Hook. Without this Hole or Casement opened, at a convenient distsnee, (that itn. z 8 . f. 741. ma y not be perceived by the Company in the Röom) place the Picture orObject, ‘which you will Reprefent, Inverted, and 'by medras of Looking-Gkslesplaced behind, if the Picture be transparent, Reflect the Rays of the Sun ft>,as that they may pals through it towards the .place, where it is to be Repre-sented ; and to me end that no Rays may pafs be sides it, let the Picture beencompaffed on every side with a Board br Gloath. If the Object be a Sta-tue, or some Living Creature, then it must be very much Enlightned bycasting the Sun-Benms ön it by Refractioh, Reflexion, or both. BerWeen thisObject and the Place where ’tis to be Reprefented, there is to be placed abroad Convex Glafs, gröund of ! Iuch a Convexity, as that it fnay Repteikntthe Object Distinet on the (aid place ; which any one, that hath any Infightin the Optick?, may easily dircct. The nearer it is plaCed to the Object, themore is the Object magnified on the Wall, and the further off tbe lefi ,which dtversity is estected by Glaffes of severa l SphCrCs. Ii the Obj&ct <an-not be Inverted (as ’tis pretty diffieult'todo with Erving-Änimals, C&rklies, @?c.)'then there must be tWo large Gktsies of -ebnvetiient SphCfcs, and -they 'placedat their apptopriated Distances, (whiclttare very-eafily-fofrnd by Trials) (b asto make the Reprclentations Erecr, äs well - as the Object.

These Objects, Reflccting and Refracung Glaffes, and the whbie -Appara-tus ; as also the Perlons eniployed to Order, Chänge, and marke use of them,muff be placed without the faid high Window ör Hole, so fluat they fnaynot be perceived by the Spectatorsdn the Room z ;ind fnewhole Operation-"will be easily performed.

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