Kinahan — On Irish Arenaceous Rocks. 535 



stones as found in situ in the island, or if rough agates that 

 afterwards were stained. In the Ballinascreen Hills, northward 

 of Draperstown, Co. Londonderry, the " chalk conglomerate," 

 the basal bed of the Eocene, is in a great measure made up 

 of broken flints, that were baked by the subsequent over- 

 flow of basalt. In all the naturally stained agates I have 

 seen the colours developed are shades of red, they being of the 

 " carnelian " type, as may be seen in the flint fragments in situ, 

 and in the flint implements found in the valley of the Lower 

 Eann, Co. Londonderry. Symes states that the agates of this class 

 are common everywhere in the North of Ireland, where the basalt 

 lies direct on the Eocene basal conglomerate, that is the rock due 

 to the breaking up and re -arrangement of the surface of the lime- 

 stone. He suggests that the staining is due to an iron solution, 

 combined with the baking due to the overflow of hot basalt. The 

 process must be more or less allied to the artificial production of 

 " carnelian s ; " but as the natural ones are more opaque than the 

 •artificial, an iron solution, as suggested by Symes, may be present. 

 At present we are unable to say if the Eathlin " onyx " and " sar- 

 donyx," as seen in the Science and Art Museum, Leinster House, 

 Dublin, have been procured in situ, or if they were afterwards 

 artificially stained. The stones, however, whether naturally or arti- 

 ficially stained, give such good results, that they ought to be 

 worth looking after; not, however, for a trade in the island in 

 cutting and polishing, for labour is so cheap in Germany that it 

 would be impossible to compete therewith ; but the raw material 

 might be exported to Germany, as it is at the present time 

 from the River La Plata. 



[In the "Geology of India," Pt, iii., pp. 506, &c, Ball gives an interesting 

 and exhaustive account of agates, and how the colours are produced. Many of the 

 raw Indian agates are identical with those from Antrim, while their origins seem to be 

 very similar, both being baked by overflow of basalt. Besides being used for orna- 

 mental purposes, they are largely manufactured into burnishers.] 



Sand and Gravel. — As a subordinate adjunct of the flows 

 of Eocene basalt, Lewis records a rough tripoli found at Agnew 

 Hill. 



In various places in connexion with the Drift, the alluvium and 

 the diluvium, are sands and gravel. In the drift near Ballycastle 



