Messrs Peach & Home on Old Red Smidstone of Shetland. 81 



terised that period. Though the areas now occupied by the 

 sedimentary rocks are limited in extent, there can be little 

 doubt that they convey but a faint impression of the original 

 extension of this formation in the Shetland Isles. The fine 

 mural precipices of Old Eed Sandstone which are visible in 

 some of the islands, notably in Bressay and Foula, furnish a 

 striking proof of the importance of the relics which have 

 escaped denudation. 



As far back as the year 1811, Dr Fleming pointed out the 

 occurrence of vegetable impressions in the sandstones of 

 Bressay, in a paper published in the Memoirs of the Wer- 

 nerian Society, vol. i, entitled, " A Mineralogical Account of 

 Papa Stour." Since that time numerous plant remains have 

 been found in the members of this formation at different 

 localities in Shetland. 



In 1853 Dr Hooker referred some plant remains collected 

 from the Lerwick sandstones, by the Eight Hon. Henry 

 Tuffnell, to calamites ; while, in 1858, Sir Eoderick Murchison 

 intimated the discovery of Estheria in the Lerwick beds, 

 which linked these strata with those of Caithness and 

 Orkney. 



Dr Hibbert, in his admirable work on the Shetland Isles, 

 laid down approximately the limits of the different Old Eed 

 Sandstone areas. In 1877 Dr George Gibson published a 

 thesis descriptive of these rocks ; and in 1878 Professor 

 Geikie, in his exhaustive monograph on the Old Eed Sand- 

 stone of the North of Scotland, described the relations of the 

 Shetland representatives to the other members of this forma- 

 tion in Orkney and Caithness. He refers specially to the 

 proofs of volcanic activity in Papa Stour, the geological 

 structure of whixih is given in detail. 



During the summer of 1878 we made some traverses in the 

 islands for the purposes of determining the disputed question 

 of their glaciation, and in the course of these traverses we felt 

 it to be necessary to map out with as much minuteness as 

 time would permit the boundaries of the various Old Eed 

 Sandstone areas, on account of the important evidence which 

 they furnish regarding the movements of the ice in the 

 glacial period. We were induced to work out the order of 



VOL. V. F 



