and, on its left, Dalhousie Burn, and flows past Newbattle Abbey; the northern rises in the Pentlands, and proceeds through much picturesque scenery past Penicuik, Roslin, Hawthornden and Lasswade; the two streams uniting within the grounds of Dalkeith Palace. Braid Burn from Capelaw Hill passes between the Braid Hills and Blackford Hill, and reaches the sea at Portobello. The Water of Leith, with its head streams on the western slope of the Pentlands, flows past Balerno, Currie, Juniper Green, Colinton, Edinburgh and Leith. The Almond, rising in Lanarkshire, and its right-hand tributary, Breich Water, form the boundary between Midlothian and Linlithgowshire. Several of these streams, especially the Esk and the Water of Leith, furnish much water power. The only loch is that at Duddingston, but there are several large reservoirs connected with the water supply of Edinburgh. Cobbinshaw reservoir, situated at the head of Bog Burn, a tributary of the Almond, is used for the supply of the Union Canal connecting the Forth with the Clyde.
Geology.—The southern portion of the county, embracing the Moorfoot Hills and a large part of the catchment basin of the Gala Water, lies within the Silurian tableland of the south of Scotland. From Bowland northwards to Crookston in the Gala valley the Silurian strata are mainly of Tarannon age and consist of greywackes, grits, flags and shales, with thin dark seams which yield graptolites sparingly. To the north of this area, older sediments, comprising Arenig cherts, black shales, greywackes and grits of Llandeilo and Caradoc age, rise from underneath the Tarannon strata and spread over the hills north to the margin of the tableland. In some of the folds of Arenig cherts diabase lavas appear, which occupy small lenticular areas. All the Silurian strata are repeated by folds striking north-east and south-west and frequently dipping in one direction, to the north-west as in the Gala valley. North of the Silurian tableland and within the area occupied by the younger palaeozoic rocks of the Pentland Hills, there are various inliers of Upper Silurian strata. These isolated patches occur (1) in the North Esk section, (2) at Loganlee reservoir, (3) near Bavelaw Castle, and (4) in Bavelaw Burn. The section in the North Esk is by far the most complete, as the strata embrace Wenlock, Ludlow and Downtonian rocks with a north-east strike similar to that of the beds in the Silurian tableland. The Wenlock rocks have yielded a rich suite of organic remains. In the Pentland Hills the folded and denuded Silurian strata are covered unconformably by Lower Old Red Sandstone rocks, comprising conglomerates and red sandstones, which are succeeded by a great volcanic series, the latter extending from the West Kip Hill to the Braid Hills. The pebbles of the basal conglomerates are derived chiefly from the underlying platform of greywackes and shales and from the Radiolarian cherts and volcanic rocks in the tableland to the south. The contemporaneous igneous rocks include olivine basalts, andesites, trachytes, rhyolites and tuffs, which are pierced by the microgranite of the Black Hill and by several vents filled with agglomerate, as near Swanston.
The Upper Old Red Sandstone rests unconformably on all older formations. The red sandstones and cornstones of this division form the Cairn Hills, and are traceable north-eastwards along the north-west slope of the Pentland Hills towards the Clubbiedean reservoir, where they are overlapped by Carboniferous strata. They occupy the south part of the city of Edinburgh, they occur in the lower slope of Salisbury Crags, and south by Craigmillar and Liberton towards Mortonhall. Recently the horizon of these beds has been proved by the discovery of fish remains (Holoptychius), a zonal form of the Upper Old Red Sandstone. The remainder of the county embracing the fertile low ground west of the city of Edinburgh and along the basin of the Esk is occupied by Carboniferous strata and various igneous rocks associated with that formation. The Pentland Hills, formed of older Palaeozoic deposits, appear as a prominent ridge, throwing off the Carboniferous beds to the north-west and south-east. In the former direction only the Calciferous Sandstone series is represented, and in the latter all the Carboniferous divisions are well developed. The lowest subdivision of the Calciferous Sandstone series, consisting of sandstones, red and green shales, marls and cement-stones, appears in the ridge of the old part of the city between the Castle and Holyrood, in the Hunter’s Bog and on the north-west side of the Pentland Hills. Intercalated in this series near the top, there are interbedded volcanic rocks, comprising olivine basalts, mugearites, tuffs and agglomerates, which form conspicuous features on Arthur’s Seat, on Calton Hill, at Craiglockhart and Corston Hill south of Mid Calder. Next in order come the Granton sandstones and Wardie shales, which are best seen on the shore at Granton, and extend up the Water of Leith in the direction of Colinton, where they are succeeded by the Hailes sandstone. The upper portion of the Calciferous Sandstone series, overlying the Hailes sandstone, embraces the valuable oil-shales, which give rise to one of the chief industries of the Lothians. Recently, however, it has been proved that some of the bands in the Wardie shales give a low yield of oil and sulphate of ammonia. The oil-shale-fields in the county lie partly along its west margin from Mid Calder south to Breich and also on the south-east side of the Pentland Hills between Straiton and Carlops along the west side of the Midlothian basin. From an economic point of view the Midlothian coalfield is of special importance, the strata being arranged in a syncline, the long axis of which trends north-north-east and south-south-west. In the centre of the basin lie the Coal-Measures covered by the barren red sandstone of Dalkeith, probably on the same horizon as the red sandstones of Wemyss in Fife (Middle Coal-Measures). The underlying Millstone Grit and Carboniferous Limestone series with its middle-coal-bearing group rise from underneath the Coal-Measures, forming parallel bands curving round the basin. Along the west side of the syncline, the strata dip at high angles to the south-east, are sometimes vertical and even in some cases inverted, while in the centre they become flat and rise at gentle angles towards the east. The Coal Measures and the coal-bearing group of the Carboniferous Limestone series contain numerous valuable coals and ironstones, and there still remains a large field for development. The intrusive igneous rocks forming prominent features in the county are divisible into two main groups, which are separated from each other by a considerable interval of time. The coarse agglomerate filling the old volcano on the top of Arthur’s Seat is associated with the eruption of the volcanic rocks of Calciferous Sandstone age near Edinburgh. The fine grained basalt appearing as a plug on the Castle Rock closely resembles the basalt on the top of Arthur’s Seat, and is likewise of the same age. The intrusive sheets of Salisbury Crags and Corstorphine Hill composed of olivine-dolerite belong to the same general period. But the quartz-dolerites represented by the Ratho sill are in all probability of late Carboniferous age.
Climate and Agriculture.—In the hill country the average rainfall is 37·4 in., but on the coast only 28·4 in. The average temperature ranges from 38° F. in January to 59°·5 in July, the mean for the year being 47·7. The north-east and easterly winds prevailing in spring are, especially in Edinburgh and its vicinity, remarkable for their cold and blighting character. Excepting in the uplands, snow seldom lies long, but frosts sometimes occur at night as late as the beginning of June, and severe enough to destroy the young shoots of seedling trees in nurseries. But the winter is often astonishingly mild. The common snowdrop (Galanthus nivalis) blossoms as early as the 25th of January, the kidney liverleaf (Hepatica triloba) by the 31st of January and the rhododendron (R. nobleanum) by the 25th of February. On the shores of the Forth along the Almond and the Esk, and on some of the richer flats, grain crops ripen early; 2 m. nearer the hills and 200 ft. higher the harvest is ten days later; and at 600 ft. still another week later. High farming is the rule in the three Lothians. All the area on which wheat can be profitably grown is so occupied; oats, however, is the predominant grain crop, though barley is also raised. Turnips and potatoes are the chief roots, and beans are grown to a limited extent. A large area is occupied by pasture and sown grasses, fallow land having practically disappeared. Near Edinburgh sewage farming has been largely developed. There are 200 acres at Craigentinny between Restalrig and the Forth, besides smaller tracts under similar treatment at Lochend, Dalry and the Grange. The produce consists principally of natural grasses. Sheep and cattle raising is an important pursuit. In the neighbourhood of the capital dairy farming is conducted on an extensive scale. Horse breeding flourishes, several of the studs being of excellent character, Clydesdales predominating. Pig-keeping has grown considerably and poultry-farming is carried on near Edinburgh. The nursery gardens are extensive, and, besides market gardening, which prospers near the capital, there are many orchards.
Other Industries.—Though as a whole not a mining county, Midlothian possesses some mineral wealth. Coal is extensively mined at various points on the North Esk, like Penicuik, Loanhead, Bonnyrigg, Eskbank and at Gorebridge, Newbattle, Newbigging, Niddrie, Gilmerton, Mid and West Calder. Ironstone is obtained chiefly at Lasswade and Penicuik and fire-clay occurs at various points. In the vicinity of West Calder there is a large amount of valuable oil-bearing shale. Limestone is of frequent occurrence—at Esperston, Cousland, Crichton near Dalkeith, Burdiehouse, Gilmerton near Edinburgh, the Camps in Kirknewton parish, and at Muirieston and Leven Seat in the south-west. Freestone is quarried at Craigleith, Hailes, Redhall and Craigmillar. It is used for pavements and stairs, and for the great docks at Leith. Barnton Mount supplies large blocks
