THE OLD RED SANDSTONE OF THE ORKNEYS. 391 



curiously enough, received hitherto by far the greatest share of attention. This is due, 

 without doubt, to the number and excellent preservation of their fossils, of which Hugh 

 Miller was led to make the somewhat hyperbolical statement, that were the trade once 

 fairly opened, they could supply with ichthyolites, by the ton and by the shipload, all the 

 museums of the world.* The list of collectors who have searched these beds is a long 

 one, and includes many eminent names, — Hugh Miller, Professor Traill, Mr C. W. 

 Peach, Mr W. Watt of Breckness, the Rev. J. H. Pollexfen, Dr Clouston, to mention 

 only a few of those who, in a previous generation, were the first to develop their 

 palseontological resources. The district to which they are confined is compact and of 

 no great area, lying mostly in the West Mainland, in the parishes of Stromness, 

 Sandwick, Birsay, and Harray. If to this we add the flagstones which unconformably 

 underlie the sandstones of the west end of Hoy, and those also around the granite area 

 in Graemsay, we include the entire district from which have been obtained the many 

 Orkney fossils which are deposited in the museums of the world. The rest of Orkney 

 is a district relatively barren and uninteresting to the collector, with the exception of 

 certain areas of the Eday sandstones, such as Deerness — where, indeed, the abundance 

 of the fossils hardly compensates for the paucity of specific forms. 



The granite of Stromness. — Professor Jameson seems to have been the first to 

 recognise the relation between the ancient crystalline rocks of the granite axis of 

 Stromness and the flagstones of Old Red Age which rest on them by means of a thin 

 basal conglomerate. As it has already been more than once described, a brief notice 

 here will suffice. The area occupied is elliptical in shape, and stretches from the Ness 

 of Stromness to the Point of Inganess on the west coast, a distance north-west of about 

 five miles, with a breadth of about a mile. In the hand specimen it is mostly a pink, 

 sometimes a grey granite, of medium grain, and with only a black mica. In many 

 places it is markedly schistose, as at the Ness of Stromness and behind the town, some- 

 times passing even into a flaggy garnetiferous t mica schist. Numerous veins traverse 

 it, fine-grained elvans and quartz porphyries, with stony matrix and large quartz 

 phenocrysts, and very coarse pegmatites, usually without mica, and showing traces of 

 graphic structure. The microscope shows the rock to be a pretty normal granitite, 

 with orthoclase, plagioclase, and microcline (in small quantities), quartz, biotite, and, 

 especially in the segregation veins, occasional micropegmatite. Sections cut from the 

 gneiss show it to be of similar constitution, but the pressure twinning of the poly- 

 synthetic felspars and the strain shadows in the quartz show that in these bands the 

 rock has been subjected to a deforming force. 



The basal conglomerates. — Wherever the actual contact between the granite and 

 the flags is exposed, it proves to be an unconformable junction, the rock immediately 

 resting on the granite being always a conglomerate composed of fragments of the 

 crystalline rock. Admirable sections are to be obtained at the Ness of Stromness and 



* Hugh Miller, Footprints of the Creator, p. 2. 

 t Heddle, Geognosy of Scotland — ' Orkney,' p. 135. 



VOL. XXXIX. PART II. (NO. 13). 3 



