C. LAPWOETH ON THE HOEEAT SEMES. 243 



paper I shall therefore restrict myself to the enumeration and dis- 

 cussion of such facts regarding their physical and zoological relation- 

 ships as may be gathered within the single area where they are 

 most perfectly exhibited, and which may conveniently be denomi- 

 nated the Moffat district. 



§ II. General Characters of the Strata of the Moffat District. 

 (Plate XI.) 



The district included under this title is a rectangular area about 

 25 miles in length and 8 miles in average diameter, lying almost in 

 the geographical centre of the South-Scottish Silurians. A small 

 portion of the northern half of the area is included in Peeblesshire ; 

 the remainder is almost equally divided between the two adjacent 

 counties of Selkirk and Dumfries, the line of demarcation between 

 them running in an irregular curve transversely through its centre. 



As a whole, the district may best be considered as embracing that 

 portion of the rolling tableland of South Scotland lying immediately 

 to the north-east of the upper reaches of the fertile vale of the An- 

 nan, which, roughly speaking, forms its abrupt western boundary. 

 In every other direction it merges imperceptibly into the sea of 

 rounded heights and hollows that constitute the Southern Uplands. 

 The county boundary already referred to marks the position of the 

 watershed between the head waters of the streams draining into the 

 Irish Sea and those which flow into the German Ocean. This ridge 

 includes the most elevated ground in the south of Scotland, its cul- 

 minating points, White Combe, Hartfell, &c, exceeding 2600 feet 

 in height. The burns that descend its northern slope unite to form 

 the Tweed and its tributaries, the Yarrow and the Ettrick; those to 

 the south are all feeders of the Annan. These numerous mountain- 

 streams have eroded the ancient plateau into a perfect maze of 

 narrow valleys, many of which, especially those of Blackshope, 

 Carrifran, Gameshope, and the Talla, are bounded by abrupt or pre- 

 cipitous cliffs, and afford striking examples of upland scenery. 



The district is cleft longitudinally through its centre, from end to 

 end, by a deep narrow valley, along which passes the highway from 

 Selkirk to Dumfries, forming the only means of intercommunication 

 between its sparsely scattered inhabitants. The western half of this 

 hollow is constituted by the picturesque pass of Moffatdale, which, 

 bounded on both sides by a line of bold heights, runs in a perfectly 

 straight line ten miles in length from the Annan to the watershed 

 at Birkhill. To the east the hollow is continued by the tortuous 

 gorge of the infant Yarrow ; this, widening as it descends, embosoms 

 the lonely lake of St. Mary's, and ultimately passes out of the dis- 

 trict into the cultivated haughs of the more populous area of Ettrick 

 Forest. 



The lowlying flats of Annandale are formed of the relics of Per- 

 mian deposits ; but all the upland portions of the Moffat district are 

 carved out of the grey, intractable Silurian grits and flagstones 

 already so frequently referred to. Beyond a clearly marked ten- 



