5^^ Experiments and Obfervatlons 



fpoken of in the ciefcription of the other fpecimen. This fub- 

 ftance is mixed with tiie iron in fuch a manner, that if the 

 whole of the former could be removed, the remaining part 

 would confiR merely of iron in the metallic (late, and would 

 prefent the fame cellular appearance as the preceding fpeci- 

 men, and the ramilied or cellular part of the fpecimen now 

 uefcribed. 



This ftony part, feparatcd from the iron, appears in the 

 form of fmall nodules, generally of an irregular (hapc, but 

 fomclimes nearly globular : they have a perfeftly fmootli and 

 fliining furface, fo as very often to preient the appearance of 

 fmall balls of glafs ; a circumftance that has led many perfons 

 to fuppofe them the refult of a real vitrification. Some of 

 thefe nodules have feveral irregular facets, produced by the 

 compreflion of the iron in which they were inclofed ; but I 

 have never obferved in them any appearances that could lead 

 nie to fufpect they had the flighteli; tendency whatever to 

 aflTumc a determined cryftalline form. 



This fubftance is always more or lefs tranfparent. It b 

 fufficiently hard to cut glafs, but has no effeft upon quartz. 

 It is very brittle : its fraiture is ufually conchoid ; but I could 

 perceive that it broke in any particular direction, in fuch a 

 •way that I could confider the frafture as a natural one. It 

 becomes electric by fri£lion. Its fpecific gravity is from 3263 

 103300, It is very refradtory : I kept it, for fome lime, ex- 

 poied to a degree of heat fufficiently ftrong to oxidize, to a 

 confiderable depth, the iron crucible in w hich it was placed, 

 without its having undergone any alteration, except that of 

 having acquired a greater degree of intenfity in its colour. 

 Its tranfparency was not at all dimini(bcd. I think, there- 

 fore, there is not the fmalleft reafon to allow anv probability 

 to the opinion that it ought to be confidered as a kind of glafs. 



Of all fubftances hitherto known, that with which it feems 

 to have the greatell analogy is the peridot, (the chryfolite of 

 Werner,) to which fome mineralogifts have referred it. The 

 refult of Mr. Howard's analyfis of it is nearly the fame as 

 that of the analyfis of the peridot made by Mr. Klaproth. 



The hardnefs and infufibility of this fubfliance are nearly 

 the fame as thofe of the peridot ; but it feems to have a rather 

 lefs degree of fpecific gravity : that of two very perfedl cryftals 

 of peridot I found to be from 3340 to 3375. The cryfi:alline 

 forms of the fubftance here delcribed, if ever we (liould be 

 able to determine them, would clear up our doubts refpefting 

 the analogy between the two fubftances. If we confider the 

 compa£l part of the fpecimen now treated of, particularly the 

 ftrong conueclion that appears to exill between the iron and 



the 



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