THE GEOLOGIST. 



occupies the Nortli-eastern Highlands and a great portion of the eastern coast of 

 {Scotland ; fifthly, tlie Old Red series, arranged by the author into tliree divisions, 

 the middle being the Caithness flags. 



In the past autimm Sir Roderick, feeling that several points required stricter 

 examination, revisited the country already described, extending his researches both 

 east and west, and to the most northernly point of the Shetlands. 



In this tour he not only confirmed his views previously announced with regard 

 to the succession of the older rocks, but examined the structure of the Orkneys 

 and Shetlands, moi-e clearly defining the relations and physical characters of the 

 beds there composing the Old Red series. 



The present memoir comprised the details of these later observations ; and Sir 

 Roderick acknowledged the aid he had derived from Mr. Peach (Avho accompanied 

 him throughout the journey), JMr. John Miller, Rev. Mr. Gordon and others ; and 

 he referred to the previous memoirs of Mr. Cunningham and Hugh Miller on 

 Sutherland, &c., and Dr. Hibbert on the Shetland Islands. 



The principle points dwelt upon in this paper were — 



1. The evidence obtained at various points, that the Lower Silurian limestone 

 is intercalated in quartz-rock (east of Loch Eriboll, Ass}iit, &c.). 



2. That the Durness limestone lies in a basin sup]30rted by quartz-rock on the 

 east as well as on the west. 



3. That certain igneous rocks connected with the Durness trough are pro- 

 truded near Smo, -which had not before been noticed 



4. On this occasion corroborative evidence was adduced of the conformable 

 superposition of the micaceous schists or gneissose flagstones to the quartzite 

 series, the succession being visible at intervals in all the intermediate country 

 between Loch Eriboll and Ledmore, and the passage upwards from the quartzites 

 and their associated limestones into the schists and micaceous flags being both 

 clear and persistent, with some local interruptions only of igneous rocks. 



5. That the protrusion of porphyry, liypersthene, greenstone, &c. is not peculiar 

 to any one line, but occurs in the piu'ple or Cambrian sandstone, in the overlymg 

 Silurian limestone of Durness, and again in the still higher micaceous flagstones ; 

 and that the latter, when intruded upon by granite, much resemble the old gneiss. 



6. With regard to the Old Red series of the east coast. Sir Roderick pointed 

 out the extension of the middle set of deposits, namely, the Caithness flags,— 

 their great thickness in Caithness compared with their development in the south, 

 — and their range over the Orkneys into the Shetlands, where they also thin out, 

 putting on a somewhat different litliological character, and where the Old Red 

 series is chiefly represented l\y sandstones, the upper part containing plants. He 

 dwelt upon the great value of the Caithness flags as pa^'ing-stones, tlieu- extraordi- 

 nary durability being due to a certain admixture of lime "and bitumen (the latter 

 derived from fossil flshes) with silica and alumina, whilst in some parts they con- 

 tain bitumen enough to render them of economic value. The author next pointed 

 out the passage of the Caithness flags upwards into light-coloured sandstones, 

 which eventually form the great headlands of Dunnet and Hoy, where such over- 

 lying sandstones cannot be of less thickness than 1,'200 to 1,500 feet. 



With regard to the micaceous rocks of the north-east of Scotland and the Shet- 

 land Isles, they are, according to the author, portions of the series which is younger 

 than the fossiliferous Lower Silurian rocks of tlie west of Sutherland,— the so- 

 called gneiss of the Sutors of Cromarty belonging, in Sir Roderick's opinion, to the 

 micaceous-flag series of eastern Ross-shire ; and the gneissic rock extending 

 southwards to Flowerburn, Kinordy, and Roseniarkie, near Fortrose, is regarded 

 by him as a member of that series," altered by the intrusion of gTanitic and fels- 

 pathic rocks. 



The paper was illustrated by a large series of rocks and fossils collected during 

 tlie author's last tour, and by geological ma]^s, and coloured views and sections. 

 Dcccinlni- I."), 18:)S. Vw^l rUiliips. President, in the Chair. 

 The following coiumunicatlons wove vo;ul : — 



1. " On the Succession of Rocks in the Nortliern Highlands." By John Miller, 

 E>sq. Connnunicated by Sir 11. 1. Murchison, Y.P.G.S. 

 Mr. Miller in this communication explained the history of our knowledge of the 



