Burning-glass
A burning-glass is a large convex lens, which can focus the sun's rays on a small area and so ignite materials. Used in 18th century chemical studies for burning materials in closed glass vessels where the products of combustion could be trapped for analysis. A useful contrivance in the days before electrical ignition was easily achieved.The technology of the burning glass has been known since antiquity. Aristophanes mentions the burning-lens in "The Clouds," and Archimedes, the renowned mathematician, was said to have used a burning glass in 212 B.C. when Syracuse was besieged by Marcellus. Archimedes constructed a burning-glass on a scale of such magnitude that by means of it the Roman fleet was set aflame, though eventually when the city was taken, he was found among the slain. The legend of Archimedes gave rise to a considerable amount of reseach on burning glasses and lenses until the late 17th century.
Recent excavations at the Viking harbor town of Fröjel, Gotland in Sweden have revealed that this technology of fire-starting was known in the Viking Age as well. Rock crystal lenses produced at Fröjel in the 11th to 12th century via turning on pole-lathes have been found that have an imaging quality comparable to that of 1950's aspheric lenses. The Viking lenses quite effectively concentrate sunlight rapidly enough to ignite fires.
"This evening?"
"Yes!"
Brandon was sorry to say she decidedly could not.
"You might call on one of your Judges, Brandon."
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promise me to do so, Brandon?--Or a magistrate! A magistrate would send
in this dreadful extremity. It will be the death of my poor brother. I
notions are of blood."
Brandon tipped Adrian a significant nod to step in and aid.
"What is it, aunt?" asked the wise youth. "You want them followed and
quiet, Adrian, and let me speak. Brandon! it cannot be! it's quite
I never will believe it! The law cannot be so shamefully bad as to
beckoned to the old gentleman.html">gentleman. "Grandpapa! pray do make Brandon speak.
man, do you think I would stand here?"
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they none of them know anything till they join issue and go into Court.
have to keep a large supply of wigs on hand."
"And you can jest, Adrian!" his aunt reproached him. "But I will not be
to disgrace his family and ruin himself like that, and nothing shall
answer to my questions, and please to forget you are dealing with a
what he has done legitimate? Is he bound for life by what he has done
very delicate, you see, Helen."
"You're to forget that," Adrian remarked.
"A--hm! well!" pursued Brandon. "Perhaps if you could arrest and divide
to have been of unsound mind.html">mind."...
"Oh! there's no doubt of his madness on my mind, Brandon."
"Yes! well! in that case... Or if of different religious persuasions"...
.
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