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XLIX. 



NOTES ON SOME ASSAYS FOE GOLD OF EOCKS OCCUEEING 

 IN THE NEIGHBOUBHOOD OF DUBLIN. By Professor 

 JOSEPH P. O'EEILLY, Eoyal College of Science, Dublin. 



[Eead February 10, 1890.] 



The existence of gold in this country, the conditions under which 

 it has been found, as well as the localities where it has been met 

 with, are matters which have been detailed in different well-known 

 works — one of the most remarkable circumstances connected with 

 the occurrence of the metal in Ireland being the rarity of its- 

 appearance in the rock in situ, in any appreciable quantity capable 

 of giving rise to mining operations. Considering, however, the 

 varied nature of the geological formations of this Island, the 

 remarkable development of crystalline rocks, and of the older 

 sedimentary strata, the frequency of disturbances such as faults, 

 dykes, &c, it might reasonably be expected that gold-bearing 

 rocks should be met with in Ireland, and have been dis- 

 covered long ago. Nothing, however, can be collected from the 

 historical records of the country pointing to the knowledge of 

 such rocks, and it is generally assumed that the gold which cer- 

 tainly was worked in different districts of Ireland in former ages, 

 was of placer origin — that is, it was collected by washing sands 

 or the detritus of rocks accumulated by the action of streams and 

 rivers. Yet, no fact is more distinctly established scientifically 

 than the extent to which gold is dispersed throughout the rocks 

 and minerals forming the surface of the earth. Some facts in 

 this respect are worth citation. Landrin, in his work on gold 

 (Traite de l'or) makes the following statement (p. 49) : " Gold is 

 one of the most generally disseminated of metals ; there is no- 

 earth nor sand which does not contain some of it." It is found 

 even in the ashes of vegetables. Berthollet was able to extract 40 

 grains from a cwt. of ashes (= 0, 000054.) Sage went farther and. 



