Pr'mcc Rupert's Drop, or Glass Tear. 3p 



k always sufficient to justify itself, and consequently does 

 not need any apology. I therefore proceed. 



The pyrometer long ago has demonstrated to the satis- 

 faction of every one in the least acquainted ihcre.with, that 

 all bodies, whether In a fluid or solid state, expand by heat, 

 and contract by cold, and from a very obvious cause ; viz. 

 •because the particles of that fluid element, (fire,) by insi- 

 nuatino- themselves between the component parts of such 

 bodies, not only iiH the most minute interstices, and per- 

 vade everv pore with the greatest facility, but absolutely dis- 

 imite or separate the constituent particles themselves, and 

 thereby make them, in the aggregate, of a greater volume ; 

 and ultimately render such substances (if capable of fusion) 

 a fluid, or running mass : in which state such substances 

 occupy their greatest possible extension, — unless they were 

 volatilized, or changed into vapour. 



Thus much for the laws of fusion themselves. The ap- 

 plication and inferences from them are quite apprapriate. 



Tt is while the greatest possible degree of expansion of 

 the vitreous matter exists, that the portion which forms this 

 molten tear or drop I am about to treat of, is separated and 

 made. In fact, its fusion is the radical consequence of its 

 extreme rarefaction, or expansion, being physically and me- 

 chanically superinduced thereby. For, by the introduction 

 of the accumulated igneous particles, a separation of the 

 once continuous particles of the glass takes place, until the 

 attraction of cohesion entirely ceases, and fluidity eventually 

 ensues. 



Now, at this instant of extreme excitation it is, that, with 

 a sudden and forcible jirk, the artist ejaculates or throws it 

 forth to be suddenly quenched in cold water ; when it is 

 ■evident, that the parts which first came into contact with 

 the water will become cooled and indurated first, — which is 

 the exterior surface. And this stratum (if I may so speak, 

 and suppose the whole composed of a number of strata) 

 havinc taken its form and dimensions, no internal nmtation. 

 or exertion it is capable of can either alter or lessen its form. 

 But as all bodies, as was said before, must contract in cool- 

 ing, the interior parts (contrary to gradual cooling) must 

 ^ivc way : they therefore become vacuous, of necessity^ 

 And because the central parts cannot coalesce, they being 

 the last which feel the refrigerating quality of the water, 

 they remain longest in a fluid state : and as there is not a 

 sufficient quantity of matter, when cooled, to occupy all 

 the space it did when in an ignited or rai^eficd state, th* 

 parts which are most; fluid, being most easy to move, and 

 Y £ findmg 



