Page:Theophrastus - History of Stones - Hill (1774).djvu/269

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away before they get it. In Phœnicia and ^[1]Syria alſo they have a Gypſum, which they make by burning certain Stones. They have a Gypſum in Thuria too, in great Plenty; as alſo about Tymphæa, and in the Country of the

36. c. 24. Omnium autem optimum fieri compertum eſt e lapide ſpeculari ſquamamve talem habente.

↑ The Syrian, or third kind of Gypſum, this Author here obſerves, was made by burning certain Stones, which he afterwards very well deſcribes, and which we may fee from his Account were of the very Kind with thoſe we now principally uſe for that Purpoſe, and call Parget, or Plaiſter-ſtone, different kinds of which are dug in Derbyſhire and Yorkſhire in England, and the Pits of Montmartre in France. There are many other Kinds in different Parts, both of France and England, very little different from theſe and from each other; but in general all of them very well anſwer the Deſcription Theophraſtus gives of the Stones from which what I have called the Syrian Gypſum of the Antients was made.

It is to be obſerved that we, as well as the Antients, burn many very different Stones into our Gypſum, or Plaiſter of Paris, as it is commonly called; ſome of which are of the Nature of the foliaceous, others of the fibrous Talcs; others compoſed of Matter ſeeming the ſame with that of the Talcs, but amaſſed together in a different Form, being neither fibrous nor foliaceous, but ſeemingly in a coarſe Powder, or arenaceous Particles of uncertain Figures, and held together in the ſame manner as the Grit of the Stone of Strata: And finally, others truly and legitimately of the Alabaſter kind; in many of theſe, Particles of genuine ſparry Matter alſo diſcover themſelves; and in ſeveral, the Maſſes are wholly ſurrounded with, and in many Places their very Subſtance is penetrated by a reddiſh earthy Matter: Theſe require different Degrees of burning, according to their different Texture, to bring them to the State proper for Uſe: But in moſt of them it is done in a very little Time, and by a very ſlight Calcination, in comparifſon to that required for equally altering moſt other Subſtances. The reddiſh Kinds burn to a Gypſum equally white with that made from the whiteſt. The Gypſum of Montmartre in France,

[p253-2] The Syrian, or third kind of Gypſum, this Author here obſerves, was made by burning certain Stones, which he afterwards very well deſcribes, and which we may fee from his Account were of the very Kind with thoſe we now principally uſe for that Purpoſe, and call Parget, or Plaiſter-ſtone, different kinds of which are dug in Derbyſhire and Yorkſhire in England, and the Pits of Montmartre in France. There are many other Kinds in different Parts, both of France and England, very little different from theſe and from each other; but in general all of them very well anſwer the Deſcription Theophraſtus gives of the Stones from which what I have called the Syrian Gypſum of the Antients was made.

It is to be obſerved that we, as well as the Antients, burn many very different Stones into our Gypſum, or Plaiſter of Paris, as it is commonly called; ſome of which are of the Nature of the foliaceous, others of the fibrous Talcs; others compoſed of Matter ſeeming the ſame with that of the Talcs, but amaſſed together in a different Form, being neither fibrous nor foliaceous, but ſeemingly in a coarſe Powder, or arenaceous Particles of uncertain Figures, and held together in the ſame manner as the Grit of the Stone of Strata: And finally, others truly and legitimately of the Alabaſter kind; in many of theſe, Particles of genuine ſparry Matter alſo diſcover themſelves; and in ſeveral, the Maſſes are wholly ſurrounded with, and in many Places their very Subſtance is penetrated by a reddiſh earthy Matter: Theſe require different Degrees of burning, according to their different Texture, to bring them to the State proper for Uſe: But in moſt of them it is done in a very little Time, and by a very ſlight Calcination, in comparifſon to that required for equally altering moſt other Subſtances. The reddiſh Kinds burn to a Gypſum equally white with that made from the whiteſt. The Gypſum of Montmartre in France,

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