Zwischen gläser, [274-275]
Printed by T. and A. Constable, Printers to His Majesty
at the Edinburgh University Press
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[1]
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It would be quite beside the mark to search for a chemical formula to
express such a combination of silica, soda, and lime. I have little doubt that
one of the causes of this remarkable uniformity of composition is to be looked for
in the very fact that such a mixture is not a definite silicate, and is therefore the
less likely to assume a stony or crystalline structure on cooling.
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[2]
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The alumina here is probably not to be regarded as a base, but rather as
taking the place of the silica. Hence the exceptionally low percentage of the
latter.
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[3]
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It had its origin in great measure in the arbitrary regulations laid down by
the fiscal authorities at the beginning of the last century. This side of the
subject is well treated in the article on glass in the original edition of the Penny
Cyclopædia.
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[4]
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In the Museum at Kew may be seen specimens of Spanish barilla made
from the Halogeton sativa, as well as large crude cakes of roquetta from Aden and
Bagdad prepared from the Suæda fruticosa and the Salsola kali respectively.
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[5]
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‘The Processes of Decay in Glass’ is the subject of an elaborate paper by
Mr. James Fowler, to be found in the forty-sixth volume of Archæologia.
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[6]
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Good instances of both these changes may be observed in the windows and
chandeliers of the Galerie des Glaces at Versailles.
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