256 A. LIVERSIDGE. 



graph, (Plate 7, fig. 1) has not come out well and gives but a very 

 imperfect representation of the true appearance. Sp. gr. 9*73 at 

 24° C. 



An analysis was made, under my direction, of a portion of the 

 nugget by Mr. G. A. Waterhouse, B.Sc, a student in the University 

 Laboratory, who obtained the following results : — 



Gangue insoluble in H NO 3 ... ... 1 2 10 



Silver 



Gold 



Copper 



Iron and aluminium oxides 



Undetermined and loss 



97-390 



traces 



•071 



•270 



1-059 



100,000 

 By cupellation 97*27 and 97'60 per cent, of silver were obtained 

 from other portions of the nugget. 



The next section (Plate 7, fig. 2) is a section of a silver-copper 

 nugget also from Lake Superior ; the light parts are silver and 

 the dark are copper, the two metals are seen to mutually inter- 

 penetrate. The crystalline structure is not sufficiently well 

 developed in either of the metals to show it with the low power 

 of two diameters. The metals have both undoubtedly been 

 deposited from solution, but not necessarily simultaneously ; in 

 the next specimen, the associated silver has been deposited only 

 upon the surface of the copper. 



Plate 8, fig. 3) is from a photograph of the exterior of a copper 

 nugget from Lake Superior • it is an imperfect rhombic dodeca- 

 hedron of about one inch diameter, and seated upon it are small 

 imperfect rhombic dodecahedra of metallic silver of about one- 

 eighth inch across; the white appearance of the upper part of fig. 

 3 is largely due to the silver, scattered crystals of silver are also 

 seen as white patches on other parts of the copper crystal, unfor- 

 tunately they are not well formed, and they are still more imperfect 

 in the reproduction of the photographs. None of the silver crystals 

 penetrate the crystal of metallic copper ; as seen in Plate 8, fig. 4, 



