260 On the DevUrlficatim of Glass. 



aeneous substances, is the result of a conibinatlnu made at a 

 high temperature; a result which exhibits a compound per- 

 tecilv honiogcucous, more or less transparent, clastic, break- 

 ing in a particular manner, wliencc comes the name //- 

 treoiis fhuturi", a body a \erv bad conductor of caloric 

 nnd clcctr!cit\-, and susccpiibic of becoming soft at a tcm- 

 pt-Taturc inferior to that at wliich it was fused, of becoming 

 paste-like, ductile, &c. 



The phn^nohicnon, durinrr which all thc?c propertie? dis- 

 appear, is what I call dcritrijical'ion : thi.^ expression nwy at 

 lirst appear extraordinary, but it will be seen that it is pcr- 

 fcctlv inst. 



Devitritication has already been observed by various che- 

 mists ; some even have seen and remarked several circum- 

 stauces, but in an insulated manner; and I do noi know- 

 that any one has ever published a complete body of re- 

 searches proper for rendering it clear, and for proving; that 

 it is connected with all the kno<\n properties of all bodies of 

 nature, and that it is only the product of crystallization. 



Keaunmr first observed that glass, especially when com- 

 posed of diHVrcnt earths, as bottle-glass is la general^ may 

 be decomposed, and lose its transparency and all its other 

 vitreous properties. Being entirely engaged with his labour 

 oil porcelain, he was desirous of applying this discovery to 

 the fabrication of pottery, and ascribed the phaenomenon to 

 the substances in which he caused glass to cement. This 

 fact is called vcineiitathm of glass, ?ind the result, Reaumur's 

 p<ji-cc!ain. Nothing was niore calculated to retard the real 

 knowledge of this pha.'uomenon than a similar denomi- 

 nation. 



The labours of Bosq d'Antic, on the same object, were 

 midertaken ujcrely to obtain by this method a good kind of 

 pottcrv, and to thid cements bvthehelpof v.hichnew proper- 

 tii:s UJight be <iivc'n to that body. It isthusthat, bygivingthe 

 improper WAmQ ci'! coiientotiou to a phamomenon which de- 

 pcnd^d in no manner on ihc substances added as cement, 

 they mi.-led those who were induced to follow the course, of 

 the experiments befove made. It indeed results, that science 

 has gained nothing in this respect since the time of 

 Keaunmv; several ]XMSons have attempted to cement glass, 

 and uitserved nothing more in the result. 



Several persons have since observed in glass the property 

 of givmir liuth to crvstallizution ; those remarks, made iu 

 ]iaiticular by artist.> placed at the head of glass manufacto- 

 ries, have not furnished the eonscfjuences which (jught to be 

 deduced. Thcheads> uf a large establisluucnt have seldom 

 4 time 



