CRYSTALLINE STRUCTURE OF GOLD NUGGETS. 71 
solvents, such as chlorine water, aqua regia, a solution of potassium 
cyanide or by a mixture of sodium chloride solution and nitric 
acid; the last was found to be the most convenient because the 
strong solution of salt dissolved off the coating of silver chloride 
which was usually formed, and which prevented the action of the 
solvent from being properly watched. 
As a result of this treatment it was invariably found that the 
nugget did not present any traces of concentric coatings, but that 
the gold was always more or less crystallised, and in some cases 
the crystals were very large and with well defined boundaries; in 
fact the etched surfaces closely resembled those obtained from 
sections of many metallic meteorites, except in the form of the 
crystals—this structure is clearly seen in the illustrations to this 
paper. 
Some of the nuggets also showed cavities and enclosures of 
quartz, ferric hydroxide and argillaceous matter, although in 
Many cases none was visible on the rolled surface of the nugget, 
the non-appearance of the impurities on the surface being due to 
the soft gold having been usually beaten down, by rolling and 
attrition, in such a way as to cover over and hide the enclosures 
or render them less conspicuous. 
It was found also that many nuggets when heated strongly in 
a bunsen burner became blistered, and that these blisters burst 
with a sharp report sometimes accompanied by the projection of 
— pieces of gold; they also gave off gases or vapours, which 
‘ssued under considerable pressure and forced out the bunsen 
flame into little blow-pipelike jets. It was thought that these 
phenomena might be due to the presence of enclosed gases under 
Pressure, but when the nuggets showing these blisters or blebs 
were immersed in a solvent and the walls of the blebs slowly 
dissolved away, there was no escape of gas. | 
Subsequent investigations showed that the nuggets yielded but 
very small quantities of permanent gas, when examined at a high 
temperature in vacuo for occluded gases, and it was found that 
the vapour given off was mainly that of water mixed with some 
