CRYSTALLINE STRUCTURE OF SOME SILVER AND COPPER NUGGETS. 255 



nature of some of the difficulties which have to be overcome by 

 the Inter-State Commission. It is scarcely necessary to mention 

 that it is impossible in a paper such as this, to give more than a 

 bare outline of the question. It therefore seemed, on all grounds, 

 the best course to furnish a concise statement of facts and to 

 abstain from comment regarding them, and this has been the 

 course adopted. 



On the CRYSTALLINE STRUCTURE of some SILVER 

 and COPPER NUGGETS. 



By A. LlVERSIDGE, M.A., LL.D., F.R.S. 



[With Plates VII. -IX.] 



[Read before the Royal Society of N. S. Wales, August 3, 1898.'] 



In previous papers I have described the structure presented by 

 nuggets of gold, and in this, an attempt is made to do the same 

 for natural masses of two other metals ; unfortunately it is very 

 difficult to obtain nuggets of silver ; after trying for some years 

 to obtain them through most of the principal mineral dealers, I 

 have only succeeded in securing one, from Lake Superior, through 

 the late Mr. J. R. Gregory, f.g.s., of South Kensington. I 

 mention the difficulty of obtaining silver nuggets, because I have 

 to trust to the one specimen. 



It was irregular in outline and but slightly water worn, with a 

 deep cleft on one side. (Plate 7, fig. 1.) A little calcite, quartz, 

 and a few particles of native copper were found in the cavities 

 by treatment with hydrochloric acid. The section was etched by 

 means of dilute nitric acid, and presents a well marked crystalline 

 structure, the crystals are large, and most of them present a 

 satiny sheen, apparently from the reflection of light from the 

 edges of their plates. The half-tone reproduction of the photo- 



