By M. Burat'tini. n. 19.f. 348. n. 21./• 374 -

By Mr. FrancisSmethwick.n. 33- ?. 6zi.

an <AruJ\ atParis, n. 40.

I - 755 -

( '94 )

such a Cavity ; and yet more, when they shall hear the Author undertake toExcavate other such Eye 6lasses to above two Inches, and Object Glasses oflive Inches Diameter. He hath likewisc already begun his Object Glasses forthe meijtioned two Oculat ones, of the lame Figure of about two Inches Di-ameter,. which are to be lest all open, yet without caufing any Colours.

4. The Optick Glafles of M. Burattini in Poland, are perfectly wellWrought and Polilh’d. He hath fent two to Paris, but they are only theone of 1 o, the other of 8 Foot. They bear a great Aperture in relpect oftheir Length.

5- Mr. Fr. Smetbmckj having found a way of grinding Glasses not Spbe-rical, produced before the Royal Society, Feb.ij. 166 J. certain Specimina ofthat Invention, which were a Telescope, a Reading and two Burning-Glasses.

The Telescope was about 4 Foot long, fumilhed with 4 Glasses, whereofthe z Oculat ones, Plano-convex, were of this ncwly Invented Not SphericalFigure, and the 41h a Spherical Object Glass. This being compared with aeommon, yet very good Telescope, longer than it by about 4 Inches, andturned to ieveral Objects, was found by thole of the laid Society that look’dthrough them both, to exceed the other in Goodnels, by taking in a greaterAngle, and representing the Objects more exactly in their refpective Propor-rions, and enduring a greater Aperture free from Colours.

The Reading Glals of the fame Figure being compared with a commonSpherical Glals did far excel it, by magnifying the Letters to which it wasapplied up to the very edges, and by fhcwing them distinctly from one Brimthrough the Center to the other, which the Spherical Glals camc farshort of.

Lastly-, The two Buming Concaves of this new invented Figure, werethe one of 6 Inches Diameter, its Focus 3 Inches distant from the Centerthereof; the other of the lame Diameter, hüt lefs Concave, and its Focus 10Inches distant. These, when approachcd to a large Candle lighted, didfcmewhat warm the Faces of thole that were 4 or 5 Foot distant at least,and when held to the Fire, bumed Gloves and Garments at the distance ofabout z Foot from the Fire.

The Bilhop of Salisbury, Dr. Setb Ward, was by at another time, whenthe deeper of his two Concaves turned a Piece of Wood into Flame in theipace of 10 See. of Time, and the Shallower in 5 See. at most, in theSealon of Autumn , about 9 of the Clock in the Morning, the Weathergloomv. The Inventor adds, That the Deeper Concave, when held to aLucid Body, would cast a Light strong enough to Read by at a confiderabledistance; and that exposing the lame to a Northern Window, on which theSun Ihiued not at all, or very little, he had perceived that it would warmone’s hand lenlibly, by Collecting the warmed Air in the Day-time, which itwould not do alter Sun- fct.

6. We luve an Artist at Paris that Polilhes Optick Glasses on a TurnI have leen a Glals of his Workmanlhip which is very good. He turnsihcle Glasses as he does Wood, that is with the fame Facility.

7. M.Ue-