Encyclopædia americana. A popular dictionary of arts, sciences, literature, history, politics and biography, a new ed.; including a copious collection of original articles in American biography; on the basis of the 7th ed. of the German Conversations-lexicon. Ed. by Francis Lieber, assisted by E. Wigglesworth ...

338 BURNEY-BURNING-GLASS.
at Lynn, in Norfolk, in 1757, and receiv- amounts to 160 pounds. Both glasses
ed his education at the charter-house produce an effect equal to that of the
school, and the universities of Cambridge most intense fire. They kindle wood
and Aberdeen; distinguished himself which is both hard and wet in a moas a writer in the Monthly Review, to ment, and make cold water, in small veswhich he contributed mnany articles on sels, boil in an instant; metals, placed
classical literature; subsequently entered upon a plate of china, are melted and
into holy ordlers, and obtained some vitrified by them; tiles, slates, and simipreferment in the church. He died in lar objects, become instantly red-hot, and
December, 181.7; and his valuable collec- vitrified. As Tschirnhausen's glasses,
tion of books, many of them enriched with however, are not perfectly clear, and the
manuscript notes, was purchased by par- effect is thus considerably lessened, Brisliament for the British museum. B. pub- son and Lavoisier undertook, in 1774, to
lished an appendix to Scapula's Greek put together two lenses, resembling those
Lexicon fi'o-n the MSS. of doctor Askew; used for watch glasses, filling up the
a valuable edition of the choral odes of space between them with a transparent
Aschvlus, the Greek tragedian; the fluid. In this manner, veins and impuriGreek Lexicon of Philemon; remlarks on ties may be avoided, at less expense.
the Greek verses of Milton; an abridge- They succeeded in making a burningnment of Pearson's exposition of the creed; glass of 4 feet in diameter, the greatest
and a sermon preached at St. Paul's: thickness of which, in the centre, amnountbesides which he printed, for private dis- ed to 8 inclles, and which, of itself, had a
tributionD a small impression of the Latin much greater power than the glasses of
epistles of doctor Bentley and other Tschirnhausen, in connexion with a
learned scholar1s. smaller lens, or collective glass, but proBURNING-GLASS; a lens which unites duced an extraordinary effect if joined
the rays of light that fall upon it in so to a collective glass.-The experiments
narrow a space as to cause thein to kin- made by means of large burning-glasses
die any combustible matter coming in are important in chemistry and physics.
their way, like fire. T'he same name has The power of a bulning-glass, however,
been sometimes given, though improp- is almost four times less than that of a
erly, to the burning-mirror. (See the next burning mirror, or reflector (q. v.), of equal
articte.) The lenses commonly used as extent and equal curvature. This reflects
burning-glasses are convex on both sides; more light than the glass allows to pass
these bring the rays upon a point with the through it; has a smaller focal distance,
greatest force, because of the shortness and is free from the dissipation of the
of their focal distance. The effects of a rays, which takes place in the burningburning-glass are more powerful in pro- glass, since it reflects them all nearly to
pmortion as its surface is greater, and its one point, while the burning-glass refracts
focus smaller. That such a glass may them to different points. On the other
produce its greatest effect, it is necessary hand, the burning-glass is much more
that the rays of the sun should fall upon convenient, on account of the place of its
it in a perpendicular direction, which is focus, which is behind the glass. The
the case when the image of the sun, that burning point (focus) is an image of the
appears at the moment of burning, is cir- sun; its diameter is equal to the 108th
cular. If a second lens, of a smaller focal part of the focal distance, and its cendistance, is placed between the first and tre is thefocus, properly so called. In the
its focus, so aJ to intercept the rays which higher branches of geometry and conic
pass thrcslgh the first, they are still more sections, the foci are points in the parabcondensed, and united in a still narrower ola, ellipsis,, and hyperbola, where the
compass, so that the effect is greatly aug- rays, reflected fiom all parts of these
mented. The Greeks and Romans seem curves, meet. Several accidents in modto have been acquainted with burning- ern times have shown, that conflagrationsglasses, or, at least, with a kind of trans- may be caused by convex -window-glasses
parent stones similar to them. They or water-bottles. ic., which have the
became more known in the 13th century. form of buruiag-glasses, if the rays of the
At the close of the 17th, von Tschirnhau- sun are -concentrated by them upon comsen caused the largest burning-glasses, bustible substances lying within their
consisting of one piece, that are known, reach. Since the casting and polishing
to be polished with incredible pains. of large lenses are attended with great difTwo of them, still in Paris, are 33 inches ficulties, Buffon's plan of casting them in
im diameter, and the weight of one pieces, or zones, and afterwards putting