As to the nature ancl properties of it. 1 . Common 

 glass is an artificial compound of salt with sand or 

 stones. 2. It is fusible by a strong tire, and when fused 

 is tenacious and coherent. 3. It does not waste in the 

 fire. 4. When melted it cleaves to iron. 5. When red 

 hot it is fashionable into any shape, and capable of being 

 blown into a hollowness, which no mineral is. 6. It is 

 frangible when thin, fryable when cold, and transparent' 

 whether hat or cold. 7. It is flexible, elastic, and dis- 

 soluble by cold. It can be cut only by emery or a 

 diamond. 8. It is not dissoluble by aquafortis, aqua 

 regia, or mercury. 9- Neither acids nor any thing else 

 extract colour, taste, or any sensible quality from it. 

 10. It looses nothing either of its substance or of its 

 weight, by the longest and most frequent use. 1 1. It is- 

 not capable of being calcined, neither of contracting rust* 



But there is no property of glass more remarkable- 

 than its ductility, Glass-spinners draw threads of their 

 brittle matter, melting over a lamp, with far more ease 

 and expedition than common spinners do those of flax 

 or silk. These may be drawn fine as a hair, yea, as the 

 thread of a spider's w r r.b, so as to wave with every wind. 

 And the finer they are the more flexible. If the ends of 

 two such threads be knotted together, they may be drawn 

 and bent till the space in the middle of the knot does 

 not exceed the forty-eighth part of an inch in diameter* 



Near the bay of Acra, in Palestine, runs a little river; 

 now called Kardanah, supposed to be the ancient Belus, 

 famous for its sand, much used in making glass, and 

 said to have given rise to the invention of it* The 

 Sidonians are reported to have made- this discovery 

 from the following accident*. Some travellers having 

 reared an hearth on the sand of this river with large 

 pieces of nitre, and set some fern on fire under a kettle, 

 in order to boil their victuals, perceived the sand and the 

 nitre to melt and incorporate with the fern-ashes, and 

 presently after run in a transparent stream, which 

 hardened as it cooled. From hence the hint of making 

 glass was taken, which was gradually, improved to its. 

 piesent use and beauty. 



