Fauquhausox. — The. Platinum Gravels of Orepuki. 



471 



sands several crystals which, to use his own words, were minute but tolerably 

 perfect. The form was a square tablet, perfect on three sides, but irregular 

 on the fourth. With regard to this, we may say that, though we have 

 examined a considerable number of scales and samples, no such form has 

 been discovered, or, indeed, any approaching to it, and, as it has never 

 been mentioned since, the probability is it is a mere peculiarity arising 

 from sea, river, or pebble action. The scales are slightly magnetic, often 

 of fair size, some having a surface as large as that of a large pin-head. 

 Usually the surface is covered with several intersecting series of striae. 



Search has been made in Dr. Reinhard Brav^ns's " Das Mineralreich," 

 but nothing of any great importance was found, as far as the present 

 paper is concerned, on the subject of platinum. Following however, 

 his example and that of several other investigators, amongst whom we 

 may mention Professor J. F. Kemp, we took a typical scale, and, 

 after carefully polishing it, subjected it to an etching process. In this 

 the solution used was a mixture of nitric and hydrochloric acids, 

 and the strength of the etching-solution was systematically varied. The 

 scale was first of all immersed in a solution of one part of aqua regia 

 to eight of w^ater, and treated carefully for a quarter of an hour. It was 

 then washed and examined in reflected light. No alteration was, how- 

 ever, fomid. The strength of the solution was then increased gradually 

 from one part in eight of water to one part in two of water. With this 

 solution, after heating gently for half an hour, etching was noticed, but to 

 a small extent. Lastly, a solution of one part in one of water was used ; 

 the surface then became decidedly etched, but no definite pattern was 

 formed, so that it was not considered worth while to photograph it. This 

 result shows that there can be no mechanically included gold in the scale, 

 for the gold would disappear with comparatively Aveak acid. It is also 

 proved conclusively that the opinion expressed by W. S. Hamilton in the 

 paper above referred to — that the striae are caused by the scale being built 

 up of a number of smaller crystals — is without foundation. For if crystal- 

 line structure were present the etching would be sure to give evidence of it 

 in the formation of a definite pattern. 



Analysis of the Metal. 



In all investigations into the occurrence of platinum in different locali- 

 ties an analysis is of importance from both an economic and a purel}- 

 scientific point of view. The composition of nuggets, grains, or scales 

 has been foimd to be very different in different countries, and several 

 general rules can be founded on a comparison of the different results. It 

 will be interesting and ii:istructive, therefore, to compare our results with 

 those already obtained by different investigators. The method adopted 

 was a slight m.odification of the one devised by Deville and Debray. 



The results obtained from the analysis of the platinum-alloy were as 

 follow :- 



