168 Scientific Proceedings, Royal Dublin Society. 



and mica, with very little green grit fragments) point to the 

 mother rock being either a granite or highly metamorphic schist 

 or gneiss, and none of these rocks are known to occur in the 

 immediate neighbourhood. The mother rock may, therefore, be 

 some distance off, and the concentration here of the " black sand " 

 may be due to local circumstances. 



The drift in which this sand occurs is, for the most part, very 

 arenaceous, and contains very little argillaceous matter. It appears 

 to have accumulated where there was a prevalence of rapid and 

 varying currents, and may, therefore, be the washings of some 

 previously formed drift, the concentration of the sand being due 

 to the reaction of two or more currents. This question, however, 

 I would leave to more experienced observers to decide. 



Note added in the Press. 



In analyzing this sand the following method was adopted, viz. : — After 

 the gold specks were picked out several of the concentrated residues were 

 finely pulverized, mixed together, and boiled for some time in strong 

 hydrochloric acid ; this was evaporated to dryness (to expel free acid), 

 boiled for some time with water, and filtered. This filtrate, when exa- 

 mined in the usual way, was found to contain lead and copper in very 

 small quantities, iron and alumina in large quantities, chromium, zinc, 

 manganese, lime, and magnesia in small quantities. The portion in- 

 soluble in boiling hydrochloric acid was fused with potassic bisulphate 

 (KHSO4), aiitl the fused mass was dissolved in cold water and filtered. 

 This filtrate was boiled so as to precipitate titanic acid, and filtered. 

 That portion of the fusion which was insoluble in cold water was treated 

 with a little dilute hydrochloric acid and boiled and filtered. In this 

 filtrate and in the filtrate from the titanic acid, copper, iron, alumina, 

 chromium, and manganese were found. After treating the fused mass 

 with hydrochloric acid, the insoluble residue was boiled for some time 

 with caustic potash and filtered. From the filtrate tungstic acid was 

 precipitated on acidifying. The residue, after being treated with caustic 

 potash, was fused with potassic cyanide, and from the fused mass a 

 button of tin was extracted. 



