258 REPORT OF MEETINGS FOR 1905 



the rate of deposition of rock material brought in by the old 

 river, whose course here lay South-Eastward, being generally 

 balanced by the rate of subsidence. Under some such conditions 

 were formed the rocks which now constitute the slopes on 

 the West side of Hunter's Bog, and most of the deep scarp 

 extending downward from Salisbury Crags to the Queen's 

 Drive below, and which correspond in petrographical character 

 and stratigraphical position to the strata called the Lower 

 Limestone Shale on the Southern side of the Border. 



Thereafter followed a more rapid subsidence, during which 



the sea may frequently have gained admittance, 

 Volcanic although the general absence of organic remains 



Influence. forbids the entertainment of positive views on 



this point. Under these conditions was laid a 

 mass of shales and cement stones, with occasional bands of 

 sandstone, and several bands of limestone of a peculiar type, 

 composing the Ballagan Beds of Glasgow geologists. During 

 the process of their formation a volcano, or, perhaps, a series 

 of volcanoes, arose in some part of the area to the West of 

 the one now under review. The precise nature of its earliest 

 eruptions must ever remain unknown ; but proof exists that 

 while the Ballagan Beds were being laid in the area now 

 represented by the Queen's Park and the Calton Hill, the 

 volcano did now and then, early in its developmental history, 

 give rise to explosive eruptions sufficiently violent to project 

 fragments of eruptive material into portions of the areas 

 above indicated. Hence it happens that the Ballagan Beds 

 are inter-stratified with bands of tuff. Eocks so formed now 

 constitute the lower part of Hunter's Bog, and much of the 

 rising ground to the East of that depression. Concurrently 

 with the upgrowth of this volcano there arose hot springs, 

 and perhaps also geysers, from which were deposited beds of 

 calcareous and siliceous sinter, which were spread out in 

 thin layers in the vicinity of their orifices. Several of these 

 deposits occur in connection with the old Edinburgh volcano, 

 and may be seen at various places in the Queen's Park. 

 Then occurred a succession of periods of more violent explosive 

 eruption, alternately with conditions favourable for the growth 

 of beds of sandstone, which were followed by the outpouring 

 of one or more beds of basalt lava, while the area was still 



