O'Reilly — Notes on some Assays for Gold, etc. 457 



rock is formed of quartz and purple or red clay- slate pebbles, 

 cemented by a red argilaceous indurated clay resulting from the 

 erosion of older formations noted for their auriferous character, it 

 seemed reasonable to assume that the debris forming the old red 

 should show traces of the metal. Having collected specimens from 

 the Drift, and from various localities about Dublin, samples were 

 made of them and assayed for traces of gold. Both the assays 

 reported showed traces of the metal, the samples being from loca- 

 lities wide apart. The last assay was in January, 1889. 



It is interesting to note in connection with these two assays, 

 the account which appeared in the Mining Journal of September 

 28, 1889, of the "Witswatersrand Grold Field, Johannesburg, 

 Transvaal, and the further notice of this Mineral District read 

 at the Geological Society of London at their Meeting of November 

 20th last. From these two descriptions it would appear that the 

 " reefs " are in reality the outcrops of a conglomerate bed, asso- 

 ciated with red purplish rocks which present themselves stratified 

 and dipping at angles varying between 45° and 80°. As might 

 be expected, the President of the Society considered the occurrence 

 of gold in large quantities in such a conglomerate as " a remark- 

 able and interesting case." l 



So far as the description of the formation goes it seems to 

 resemble in some degree the old red sandstone of this country ; 

 and the discoveries being made in South Africa render such results 

 as those furnished by the assays quoted both interesting and of 

 some practical value as regards the future. 



As minerals rich in iron, and particularly those containing 

 pyrites, may generally be looked on as likely to show traces of 

 gold, it occurred to me to put this likelihood to the test in the case 

 of the pyrites which accompanies nearly all coals except those of 

 the very purest classes. For that purpose I collected from time to 

 time, during the winter months, samples of the ashes from the coals 

 as supplied to the College, and which it may be assumed as pre- 

 senting rather a mean quality than otherwise. The ashes were 

 washed, and the remaining heavy part was assayed by Mr. 

 Wrapson, an Associate Student of the College, under the guidance 

 of the Assistant-Chemist, Mr. Shegog. From Mr. Wrapson's 



1 See also article in the Pall Mall Gazette of Monday, February 17, 1890. 



2 M2 



