158 Craigmillar and its Environs. 



Red Sandstone times ; while there can be no doubt 

 that the porphyrites and felstones of the northern 

 end of the range were erupted during the close of the 

 deposition of the upper beds of the Old Red Sand- 

 stone and the beginning of the Carboniferous system. 

 The Mid-Lothian basin is comparatively free from 

 eruptive rocks, with the exception of a dyke that 

 cuts through the most northerly part of the basin, 

 and which, probably, is a continuation to the east 

 of one of the parallel dykes which traverse the mid- 

 land counties of Scotland west of Edinburgh. 



The environs of Craigmillar and the adjacent 

 district afford ample scope to the collector of fossils, 

 nearly all the rocks we have mentioned being fossili- 

 ferous. The beds of the Lower Silurian system are 

 but sparingly fossiliferous, although they offer a good 

 field for the geologist, and will repay the labour of 

 those disposed to devote their time to this series of 

 strata. The Upper Silurian of the Pentlands has 

 yielded a goodly number of fossils. Some fossiliferous 

 beds of this formation occur at Nine-Mile-Burn, on 

 the Pentlands, south-west of Glencorse. The Old 

 Red Sandstone of the Pentlands, so far as known. 



