Recourſe to Fire to give them their Colour; and that therefore it is not probable, the ſame Power ſhould be able to take it away; for the Truth of this, is only, that the Colour of the native Turquoiſes of ſome Countries is not equally ſpread through the whole Maſs, but lodged in different Parts of it in Form of Veins and Striæ: It is to diſlodge the Colour from theſe Veins, and diffuſe it equally thro' the whole Maſs, that they have Recourſe to Heat: A very gentle Fire is all they dare truſt on this Occaſion, and is always found ſufficient. What I would obſerve from the Whole of this is, that this Effect of Fire on the rough Turguoiſes, is a Proof that their Colour is owing to the fame Particles with that of the Sapphire; and that this diſlodging and diffuſing it through the whole Maſs, is the firſt Step toward the diſſipating and entirely driving it off; for a little too long Continuance in the ſame Heat, will, as the Workmen too often find to their Sorrow, wholly drive off the Blue, and leave the Matter colourleſs, as the Sapphire when taken from the Fire,
- I am,
- SIR,
- Your humble Servant,
- SIR,
- I am,
