Account Of The Wonderful Effects Of Two Immense Burning-glasses

Mr. de Tschirnhausen constructed a burning-glass, between three and

four feet in diameter, and whose focus was rendered more powerful by a

second one. This glass melted tiles, slates, pumice-stone, &c., in a

moment; pitch, and all resins, were melted even under water; the ashes

of vegetables, wood, and other matters, were converted into glass;

indeed, it either melted, calcined, or dissipated into smoke, every

thing ap lied to its focus.



Mr. Parker, of Fleet-street, made a burning-glass, three feet in

diameter; it was formed of flint glass, and when on its frame, exposed

a surface of 2 feet 8-1/2 inches to the solar rays. It had a small

glass fitted to it, to converge the rays, and heighten the effect. The

experiments made by it were more powerful and accurate than those

performed by any other glass. The following is a brief epitome of its

astonishing power.



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Substances melted, with their weight; Weight Time

and the Time in Seconds, which in in

they took in melting. Grains.Seconds

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Pure gold 20 4

---- silver 20 3

---- copper 33 20

---- platina 10 3

Nickel 16 3

A cube of bar-iron 10 12

--------- cast-iron 10 3

--------- steel 10 12

Scoria of wrought-iron 12 2

Kearsh 10 3

Cauk, or terra ponderosa 10 7

A topaz, or chrysolite 3 45

An oriental emerald 2 25

Crystal pebble 7 6

White agate 10 30

Oriental flint 10 30

Rough cornelian 10 75

Jasper 10 25

Onyx 10 20

Garnet 10 17

White rhomboidal spar 10 60

Zeolites 10 23

Rotten-stone 10 80

Common slate 10 2

Asbestos 10 10

Common lime-stone 10 55

Pumice-stone 10 24

Lava 10 7

Volcanic clay 10 60

Cornish moor-stone 10 60

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