199 



differ much in properties from the original brass, out of which 

 it was formed. 



The mass or ingot of brass, thus formed by the union of 

 particles at a temperature which had never reached that of 

 boiling water, and a fragment of which was presented, pos- 

 sessed on that side which had been in contact with the shaft, 

 a bright polished metallic surface, like that of the original 

 metal from which it had been formed : its other surfaces bore 

 the impress of the cavity in which it was found. It was hard, 

 coherent, and could be filed or polished like ordinary brass. 

 It was, however, perfectly i/?'///^,- and when broken, the frac- 

 ture, in place of possessing a sub-crystalline structure, and me- 

 tallic lustre, like that of the normal brass or alloy, was nearly 

 Wflc^, andofa fine grained earM// character, and without any 

 trace of metallic lustre or appearance. 



Examined with a lens, some very minute pores or cavities 

 are found throughout its substance, which is uniformly of a 

 very dark brown or nearly black colour, and devoid of all me- 

 tallic character, except when cut or filed — that is, in mine- 

 ralogical language, its colour is earthy black, and its streak 

 metallic. 



The author remarked that the observed cases of aggrega- 

 tion in solid particles, without the intervention either of a sol- 

 vent or of fusion, are extremely rare, and as bearing upon the 

 little understood subject of cohesive attraction, are of much 

 interest. 



The property of welding, which is possessed by all bodies, 

 whether metallic or not, which pass through an intermediate 

 stage of softness or pastyness previous to fusion, and is not 

 found in any substance which readily crystallizes, and hence 

 passes " per saltum" from the solid to the liquid state by 

 heat, forms a " frontier instance" of cohesive forces, being 

 enabled to act in the aggregation of bodies, by only an 

 approach to liquidity, or by a very small degree of internio- 

 bility. 



