THE INFLUENCE OF GEOLOGY ON HORTICULTURE. 



401 



At Hexham (Northumberland), in the valley of the Tyne, the Hessle 

 pear and the damson thrive over an alluvial, gravelly subsoil some 12 or 

 14 feet deep over the carboniferous rock. 



Millstone Grit has a thickness of some GOO feet. It shows itself 

 in Northumberland, Durham, Yorkshire, Lancashire, Derbyshire, the 

 northern half of Devon, and part of Cornwall, and skirts the coalfield 

 of South Wales ; it lies next below the coalfields. The soil resting on 

 it is characteristically poor, and is in some parts covered with peat moss. 



In the North of England the sandstone is fine in texture, the grains 

 of sand being small, with minute plates of mica ; in other parts the stone 

 is of a coarse texture, consisting of grains of sand of the size of mustard 

 seed, held so closely together by a clayey cement as to resist the effects 

 of the atmosphere and to form one of the strongest and most durable 

 stones for building. The surface of this formation is usually hilly or 

 mountainous, and a much greater extent is covered by moor and peaty 

 swamps than is the case with any other formation in England. The soil 

 improves where it meets other rocks rich in clay and lime. The 

 Morpeth market-garden district is situated where this formation meets 

 the mountain limestone or Yoredale rocks on the north and the coal 

 measures on the south. The ' Whinham's Industry ' gooseberry origin- 

 ated here. The apple thrives here better than in the Tyne Valley. 



The Coal Measures, estimated at 300 to 3,000 feet thick, consist of 

 alternate beds of grey sandstone, dark blue shale or hardened clay, inter- 

 stratified with beds of coal, usually with an undulating but seldom hilly 

 surface. The larger coalfields are those of Northumberland, Durham, 

 York and Derby in the north ; of Stafford, Leicester and Warwick in 

 the centre ; of Gloucester, Somerset, and South Wales in the south. The 

 coal formation generally produces very inferior agricultural land, much 

 of the soil being a yellowish clay, wet, poor, and cold, producing naturally 

 very bad herbage, principally composed of heath and ' carnation grass ' ; 

 the soil, however, is improved by drainage and liming where this is 

 practicable. In Somerset and Gloucester the coal measures are covered 

 with a reddish sandy clay, which produces a good friable soil. 



The Permian Bocks include the Magnesian Limestone, which is 

 a small-grained dolomite 100 to 500 feet in thickness, generally yellow, 

 sometimes grey, exposed in a strip five to ten miles wide, running from 

 the coast of Durham to Nottingham. The soil over it is mostly thin and 

 generally dry, naturally producing a poor, short sheep pasturage, but 

 upon which furze thrives remarkably ; as an exception, however, from 

 Staindrop to Darlington, near the River Tees in Durham, is some of the 

 best and richest grazing land in the North of England, probably due to 

 transported soil covering it and improving it. Liquorice is cultivated 

 over this rock at Pontefract in Yorkshire. 



Trentham, in Staffordshire, on the Permian red sandstone of this 

 formation, has some good orchards in the neighbourhood, in spite of its 

 nearness to the pottery fumes. 



The Triassic, or New Bed Sandstone, estimated at 500 feet thick, 

 consists of alternate layers of sand, sandstone, and marl. This formation 

 extends over a larger superficial area than any other geological formation 

 of England — from Torbay in South Devon north-eastwards into Somerset, 

 vol. xxxiv. / D D 



