48 



ME. J. AV. GEEGORY OjS" THE 



III. The Yaeiolitic Diabase. 



At the north-east end of the town of Berneck, just above the 

 uppermost bridge over the Oelschnitz, is a boss of spheroidal 

 variolitic diabase ; it is situated in the angle between the path that 

 runs beside the river to the " Colonnade " and that which traverses 

 the valley between the Badleite and the Miihlleite. Beside the 

 former path there is an excellent section some 65 yards long. The 

 main mass of the diabase is a close-grained decomposed aphanite, 

 jointed into spheroids, which vary in diameter from 80 millim. to 

 more than a metre. The diabase of the spheroids is compact both 

 in the centre and on the peripher}', but at a little distance from this, 

 and running parallel to it, is a band of variolite ; the varioles in 

 the centre of this band are usually from 2 to 3 millim. in diameter, 

 but on each side they gradually decrease in size and number, so 

 that it passes into the compact normal diabase. Thus, to quote 

 the figures in one case, — externally there is a layer of compact diabase 

 30 millim. thick; then a 50 millim. layer of variolite, and within 

 a mass of the aphanite 120 millim. across ; below there is the same 

 50 millim. of the variolitic, and 30 millim. of the compact diabase. 



Fig. 2. — Section of Variolitic S]pheroidal Diabase. 

 Footpath to the Colonnade, Berneck. 



o 





Some of the smallest of the spheroids, however, are variolitic 

 throughout. AVhen examined under the microscope with a low 

 power, the rock is seen to consist of a thick green groundmass, 

 containing a number of round white varioles, sharply marked off 



In both occur small circular vesicles filled 



from the groundmass 



