Transactions. 103 



Communications. 



I. l^e Lower Carboniferous System in Dumfriesshire. 

 By Mr James Dairon, F.G.S. 



It may be recollected that the last papers I read before this 

 Society were upon the Silurian System, with its graptolites, so 

 celebrated for their abundance, and also the beautiful state of 

 preservation in which they are found around Moffat. Among 

 the numerous places, both here and abroad, I luive seen nowhere 

 that can surpass Dob's Linn, in Dumfriesshire. I have thought 

 it might be acceptable to make a change for the night to the 

 carboniferous system. It is not very extensive in Dumfriesshire. 

 Still there are a few places worthy of a visit of the geologist. 

 Tlie carboniferous system lies on the top of the old red sandstone 

 or Devonian strata, but are known from the vast mass of vege- 

 table matter which occurs in the lower members of the carboni- 

 ferous system. It is to the fact that the chief quantity of the 

 solid element being carbon ihat the system takes it name, such a 

 mass which has formed beds of coal. Coal being only mineralised 

 vegetation finds its entry into the mass of the bituminous or 

 coal-formed shales, and gives many of the sandstones and 

 limestones of this formation a carbonaceous well marked appear- 

 ance. The system is generally divided into tlie three well-marked 

 groups — the lower coal measures or carboniferous slates, the 

 mountain limestone, and the millstone grit. The plants most 

 characteristic of the group are — Sphenopteris affmis, bifidi, S. 

 linearis, pecopteris, hetoroj^hyllum, neuropteris loshii, caloemites, 

 cannteformis, lepodostrohus variabilis and ornatus, lepidojjhyllum 

 intermedium, stigmaria fcoides and stellata, with sigillaria 

 pachyderma, and occulata with knorria of various species, and 

 favularia. 



Loxcer Coal Measures or Carboniferous Slates. — This group is 

 intended to combine all alternations of strata that lie between 

 the old red sandstone and the mountain limestone. In some dis- 

 tricts it is not so well developed. In others it attains a thickness 

 of several thousand feet. In Scotland — in Fife and the Lothians 

 — it has none of the slatey character, but consists principally of 

 thick bedded white sandstone, dark bituminous shales frequently 

 embedding bands of ironstone, thin scams of coal, and peculiar 



