Page:Cyclopaedia, Chambers - Volume 1.djvu/903



GLA

( ty )

GLA

GLASS, Vitrum, a tranfparent, brittle, faftitious Body, produc'd of Salt and Sand, by the Aftion of Fire. See Vl- trRIFICATION.

The Word Glafi is form'd of the Latin Glaflum, a Plant call'd by the Greeks JJatis, by others, Aogigneme, by the Romans, frequently, Arofion, fometimes Vitrum, by the antient Britains, Quotum, and the Englifh, Woad,

We find frequent Mention of this Plant in antient Writers, particularly C<efar, Vitruvius, 'Pliny, &c. who relate, that the antient Britain* painted, or died their Bodies with Glafi, Glajlum, Guadum, Vitrum, &c, i. e. with the Blue Colour procured from this Plant.

And hence, the factitious Matter we are fpeaking of, came to be call'd Glafi ■. as having always fomewhat of this Blueiffi- nefs in it. See Woad.

The Chymiffs hold that there is no Body but may be vi- trified, i.e. converted into Glafi — By intenfe Heat even Gold it felf gives way to the Sun's Rays collected in a Burn- ing-Glafs, and becomes Glafi. See Gold, and Burning- Glafi.

Add, that as Glafs is the Effect, or Fruit of Fire, fo 'tis the laft Effect : All the Chymifls Art, and all the Force of Fire not being able to carry the Change of any natural Body beyond its Vitrification. Whence Dr. Merret mentions it as a merry Saying of a very great Artift in the Bufinefs of Glafs, That their Profeffion would be the laft in the World : For that when God fhould confume the Univerfe with Fire, all things therein fliould be turn'd to Glafs. See Vitrifi- cation.

Nature, Character, and Properties of Glass.

Naturalifts are divided, in what Clafs of Bodies to rank Glafi — -Agricola makes it a concrete Juice : Belvacenfis, a Stone : Fallopius ranks it among the Media mineralia ; and the Workmen, when in Fufion, call it Metal. But Dr. Mer- ret with Reafon fets afide all thefe Opinions, from this Con- fideration, that all the forementioned Bodies are natural Concretes; whereas Glafi is a Compound made by Art, and never found in the Earth, as the others are.

Fallopius, indeed, contends, that Glafs is no more artificial than a Metal; and that they are both equally extrafted, or educed from other Bodies : The one from Sand ; the other from its Ore. — He adds, that tho' Afb.es be added to Sand, for the making of Glafs, yet it is falfe that they contribute to the Compofition of Glafi ; their Ufe, according to him, being only for the better extrafting of the Glafs from the mineral Stone.

This, Dr. Merret eafily confutes : For if Glafi were ex- trafted from the Stones, or Sand only, the Weight of the Metal muft be much lefs than that of the Stones alone ; whereas, it is much greater, an hundred Weight of Sand, fuf- ficing for 1 50 of 'Glafi.

In effeft, the Ames contribute a deal of Salt to the Com- pofition of Glafi— Accordingly, in Pieces of old Glafs, one may fometimes pick out Grains of Salt, eafily difcoverable to the Tafte; befide that the fineft Glafs, ftanding long in a fubterraneous Place, will moulder or refolve into its firft Ingredients, Salt and Sand, by the Decay of the Union thereof. Whence it appears that the Salt remains in the Glafi, in Specie : To which may be added that Experiment of Van Helmont. " Melt Glafs-Ttuix with Sandever, and " Water. Pour on Aqua regia, enough to faturate the " Sandever; and the Sand will precipitate to the Bottom " in the fame Quantity, and Weight, as was firft ufed. " Helm. Cap. De Terra.
 * fet them in a moift Place ; and the Glafi will refolve into

Here, then, is a true Analyfis o?Glafi ; or a Solution in- to its firft Principles, or Ingredients : The Salt being im- bibed by the Sandever, and Aqua Regia. Merret. in Ant. Ncri 2>e Art. Vitrar.

The learned, and curious Author juft mentioned, gives us the following Characters, or Properties of Glafs ; whereby it is diftinguifh'd from all other Bodies ; viz. i° That it is an Artificial Concrete of Salt, and Sand, or Stones : i° Fufible, by a ftrong Fire. 3° When fufed, tena- cious, and coherent. 4 It does not wafte, or confume in the Fire. 5 When melted, it cleaves to Iron. 6" DuBile, when red hot, and fafhionable into any Form ; but not malleable : And capable of being blown into a Hollownefs; which no Mineral is. 7 W Frangible, when thin, without annealing. 8° Friable, when cold. q° Always diapha- nous, whether hot, or cold. io° Flexible, and Elaftic. 11^ 2)i/fo ::blc by Cold and Moifture. 12 Only capable of be- ing graven, or cut with 'Diamond, and Emery. 13 Re- ceives my Colour, or Dye, both externally, and internally. 14 Not diflbiuble by ,4qua fortis, Aqua regia, or Mercury. 1 5 Neither And Juices, nor any other Matter extract cither Colour, Tafle, nor any other Quality from it. 16° It admits of polifhing. 17 Neither lofes of Weight, nor Sub- fiance by the lon^eft, and moft frequent Ufe. 18 Gives Fufion to other Metals, and foftens them. 1?° The moll

flyable thing in the World, and that which beft retains the' Fafhion given it. 20 Not capable of being calcined'. 21* An open Glafi, fill'd with Water in the Summer-time^ wil} gather Drops of Water on the Out- fide fo. far as the Water on the Infide reaches ; and a Man's Breath blown upon it will manifeftly moiften it. ii° Little Glafs Balls fill'd witK Water, Mercury, or other Liquor, and thrown into the Fife ; as alfo Drops of Green Glafs broken, fly afunder with a loud Noife. 23 Neither Wine, Beer, nor any other Li- quor -will make it mufty, nor change its Colour, nor ruft it. 24° It may be cemented as Stones, and Metals, 2 5° A Drinking Glafi, partly fill'd with Water, and rubb'd on the Brim with.a wet Finger, yields mufical Notes, higher, or lower, as the Glafi is more or lefs full, and makes the Li- quor friik and leap. — ..,,-.• ,■

For the Flexibility of Glass, fee further under Fle- xibility of Glafi.

For the Malleability of Glass, fee Malleability, &c,'

Hiftory, and Antiquity o/Glass.

De Ncri will have Glafs as antient as Job. For tliaS Writer, c. XXVIII. v. 17. fpeaking of Wifdom, fays, Gold and Glafs /hall not be equaled to it. . ,- ..

This, we are. to obferve, is the Reading of the Septua-. gint, Vulgate Latin, St. Jerom, 'Pineda, &c. For in the Englifb Verfion, inftead of Glafs, we read Cryftal ; and the fame is done in the Chaldee, Arias Montanus, and the King of Spain's Edition : In other Verfions, iyc. it is read a Stone ; in others, a "Beryl : In the Italian, Spanifh, French^ High and Low Dutch, &c. a Diamond ; in others, a Car- buncle ; and in the -Thargum, a Looking Glafs. : ..<■-. In effeft, the Original Word is Zcchucbib, front the Root Zacac, to purify, cleanfe, fhine, be white, tranfparent : And the fame Word, Exod.XXX. 34. is applied toFrankincenfe, and render'd in the Septuagint, pellucid. — Hence the Reafon of fo many different Rendririgs: For the Word fignifying, beautiful, and tranfparent in the general, the Tranflators were at liberty to apply it to whatever was valuable and tranfparent.

Moft Authors will hnveAri/lophanes to be the firft Author who mentions GlafiiThzt Poet, in his Comedy call'd theClouds, Seen. I. AS 2. ufes the Word Hyalus, J'**©-, which is now ordinarily render'd Glafs. He there introduces Sthrepfia- des, teaching Socrates a new way to pay old Debts, s?ts» " by placing a fair tranfparent Stone fold by the Druggifts, " from which Fire is ftruck, between the Sun and the Writ-. " ing ; and fo melting away the Letters thereof." This Stone: Socrates calls uW©- ; which the Scholiaft on Ariftophanes derives from u«V, to rain, from the Likenefs it bears to Ice, which is Rain, or Water congeal'd • tho' it muft be own'd the Word u«a©- is ambiguous, and fignifies Cryftal as well as Glafs : And Gorrisus relates that they had a kind of yellow Amber, tranfparent as Glafi, call'd by fome, uah©-.

Ariflotle has two Problems upon Glafi ; the firft, Why; we fee through it ! The fecond, Why it cannot be beaten ? It thefe Problems be Arijiotlc's, which the Learned doubt very- much; this would probably be the earlieft Piece of Antiqui- ty of Glafs : But the firft Author, who makes unquettion'd Mention of this Matter, is Alexander Aphrodifieus, who ufes it in a Simile : "As the Floridnefs of a Colour is feen thro' " Glafi," &c. ■;'■•.

After him the Word occurs commonly enough : Luciaii mentions large Drinking Glaffis ; and Plutarch, in his Sym- pofiacon, fays that the Fire of Tamarisk Wood is fitteft for the making of Glafi.

Among the Latin Writers, Lucretius is the firft that takes notice olGlafi. — Nifi reSa foramina tranant — £hia- lia funt Vitri.—

Dr. Merret, however, adds, that Glafs could not be unknown to the Antients ; but that it muft needs be as antient as Pottery it felf, or the Art of making Bricks : For fcarcely can a Kiln of Bricks be burnt; or a Batch of Pot- tery Ware be made, but fome of the Bricks, and Ware, will be at leaft fuperficially turn'd to Glafi : And therefore, with- out doubt it was known at the Building of "Babel.

Hence, Ferrant Imperatus, lib. 25. c. 7. "Glafi, like the ; " artificial Kind, is found under Ground, in Places where " great Fires have been. — Other Gla/fes are found in round " Clods, like Fireftone, fome brittle, others firm.SV. This " Foffil Glafi is wrought by the Americans, and ufed in- " fteadoflron. " lib. XXV. c. 7. And no doubt, but Vitrifi^ cations were more common in the antient Bricks than ours : as" they temper'd their Earth two Years together, and burnt them better. See Brick.

Pliny relates the manner of theDifcovery of Glafi— It was found, according to that Author, by accident, in Syria, at the Mouth of the River Selus, by certain Merchants driven thither by the Fortune of the Sea. Being obliged to live there, and drefs their Viftuals, by making a Fire on the Ground ; and there being Store of the Plant Kali upon the Spot ; this Herb being burnt to Afhes, and the Sand or 1 * Q_q Stones