[ 199 ]
as ſome affirm, of the Uelitis, a vitrifiable Sand, it owes its Production to the extreme Force of Fire: The beſt is that, in the making of which Flints have alſo been uſed; for beſides that they melt and mix with the running Maſs, they have a peculiar Excellence in the making the Glaſs, inſomuch that they give the Differences in the Clearneſs of the Colour.
is the Effect of the extreme Force of Fire; and that the beſt ſort of Glaſs is that in the making of which Flints have been uſed, is a Truth as much known now, as it was in the Days of Theophraſtus.
The Things of which our Glaſs is made, are, Pot-aſhes, ſome ſtony, arenaceous, or cryſtalline Matter, as Sand, Flints, or Cryſtal; and Manganeze, a ferrugincous Subſtance: To which ſome add a ſmall Quantity of pure Salt of Tartar: Theſe Ingredients are calcined into what the Workmen call Fritt; and afterwards run, by Violence of Fire, into Glaſs of different Colours and Degrees of Purity, according to the different Ingredients.
The Glaſs of the Antients was, in the different Ages of the World, in different Degrees of Purity and Excellence, according to the Ingredients of which they made it; which were Sand, Natrum, and Flints. Sand was the firſt Ingredient ever uſed or thought of for the making Glaſs; and for many Ages, there was even no other Sand uſed among the Greeks than that found clean waſhed on the Banks and in the Beds of Rivers, and this, from its Uſe, might very probably acquire the Name of Uëlitis, or Glaſs-ſand.
In the beginning of this Sentence, the other Copies of this Author have ὑελιδος. I have ventured to follow Salmaſius in his moſt rational Opinion, that it was in the Original ὑελίτιδος, and a little afterwards to give χάλικι, for what has hitherto ſtood χάλκῳ, according to De Laet; who very juſtly ſuſpects, that Flints were much more likely to be made an Ingredient in Glaſs than Braſs. And, indeed, when we conſider the many Chaſms and greater Er-
