534 Scientific Proceedings, Royal Dublin Society. 



"better than in the Co. Antrim. The principal sandstones used in 

 Belfast are given under Co. Down. 



Cretaceous. — In places, under the White Limestone {Indurated 

 Chalk), are sandstones, supposed to represent the English Green- 

 sand. These are locally known as mulatto stones. They oc- 

 casionally are firm enough to be used as building stones ; but 

 in general, as pointed out by Wilkinson, they are " too friable 

 and loose-grained to be suitable for good work." Du Noyer has 

 stated that, in the Cretaceous rocks of Colin Glen, there are some 

 fine-grained, thin-bedded sandstones, which were used for litho- 

 graphic purposes. 



Flints. — The flints in the White Limestone, as mentioned in 

 the Paper on "Marbles and Limestones" (ante, page 413), were, 

 in prehistoric times, largely used for the manufacture of arrow- 

 heads and other implements, being exported into the neighbouring 

 counties. In later times they were wrought into gun flints. So- 

 late as 1840 there was a large export of flints from the Whiterock 

 quarries, near Dunluce, to supply this trade and the Staffordshire 

 potteries. Since then flints have been exported from Glenarm 

 and other places for the English potteries and that at Belleek, Co. 

 Fermanagh ; while the Eglinton Chemical Co. grind up the flints, 

 and from the powder manufacture silicious bricks, that can stand 

 any heat, and are in great request for the lining of steel furnaces. 



Agates. — Some of the flints on Rathlin Island are ribanded, and 

 appear capable of producing beautiful " onyx" and " sardonyx," if 

 we may judge from the specimens in the Science and Art Museum?. 

 Leinster House, Dublin. As is well known, the old Greeks and 

 Romans, who ranked agates high among their precious stones, in- 

 vented a method of staining them. This for years remained a 

 secret with the Italians, till an Italian and German, at one and the- 

 same time, both agate cutters, got into trouble in Paris, and while 

 in prison together the Italian cummunicated the secret to the- 

 German. Since then the great trades in agates at Oberstein in 

 Germany has sprung up, the major portion, if not all, the rough 

 agates being imported from the La Plata River, America, the 

 German quarries falling into disuse after the American cheaper 

 supply came into the market. 



As far as we can learn, there seem to be no records of these 

 Rathlin agates in Leinster House as to whether they are the 



