126 



GEOLOGY OF ARRAN. 



they have been worn by the action of the waves. The 

 beds a a are the hard trappean ash, two to three feet thick, 



6 a 



Fig. 23. 

 Trappean Ash Beds. 



enclosing the trees; b b, seams of coal, shale, and ash, in 

 alternate layers ; c c, the stems of trees, sending down roots 

 into the bed below. " Twelve or fourteen trunks in all 

 have been observed; roots descend into the sliale, and 

 branches lie about in the beds, fully mineralized, yet having 

 the structure beautifully preserved. The large stems are 

 Sigillaria, with five or BIX. internal piths shewing the endo- 

 genous structure ; the smaller branches have been identified 

 as belonging to Sigillaria, Halonia, and Lepidodendron; also 

 AntholitJies and seed cones, Splienoptiria, and Stigmaria 

 fieoides (root of Sigillaria) have been identified. The 

 structure of the plants indicates that they grew in a marshy 

 situation; and the fine ash from the volcanic vent quietly 

 and gradually enveloped the stems." * 



The seed cones here referred to have been very recently 

 described and figured by Mr. Binney of Manchester (Tr. 

 Palaemit. Soc., vol. for 1870). They are known to be the 



* Tr. Qeol. Soc, Ql, vol. ii. p. 97-8. 



