THE INFLUENCE OF GEOLOGY ON HORTICULTURE. 



409 



The Pliocene Beds, including the Norfolk and Suffolk Crags, form a 

 narrow strip on the east coast of these counties, particularly well seen 

 at Felixstowe. The crag consists of rolled pebbles, mixed with marine 

 shells, coprolites, and teeth of reptiles, all more or less impregnated with 

 oxide of iron, giving a reddish colour. These coprolites, being rich in 

 phosphate of lime, are dug out, ground, treated with sulphuric acid, 

 thus converting the phosphate into " superphosphate," in which the 

 phosphoric acid is readily available for plants, giving better results than 

 basic slag on soil containing excess of lime such as soils over the chalk. 

 The Crag produces a fertile, loose, loamy soil. 



Boulder Clay, Sand and Gravel are materials that were transported 

 by ice or ground to powder in the bed of glaciers. This material has in 

 many places altered or modified the soil by spreading over the main rocks. 

 This has been the case on some of the chalk of Norfolk, the new red 

 sandstone in the south-east of Durham, in Cheshire and Lancaster, and 

 over some districts of the London clay. Glacial deposits exist at 

 Nottingham and Mansfield, at Hatfield in Hertfordshire, at Highclerein 

 Hants, and from Norwich to Cromer in Norfolk, but they do not extend 

 south of the Bristol Channel or the Thames Estuary. The character of 

 the soil varies with the nature of the deposit, and the preponderance of 

 clay, sand, or gravel. 



Alluvial Soils are chiefly found at the mouths of slow-flowing rivers 

 and on the sides of the valleys through which they pass. Owing to the 

 large mixture of materials brought down by the river in its course, these 

 soils are almost always fertile and easily worked, producing probably 

 larger crops aud more grass than any other geological formation. 

 Examples of these we have on each side of the Kiver Humber, and on 

 the coast of Lincolnshire. The marsh land here has been reclaimed at 

 one time or another from the sea and protected by sea walls, which were 

 first made by the Romans. The Wisbech district, near the Wash, is 

 now a most successful fruit-growing district. Here fruit has only 

 recently been introduced ; this land, although low-lying, seems to be 

 but little liable to injury by spring frost, perhaps due to being near the 

 sea. Raspberries thrive here specially well. Fruit is also grown at 

 Holbeach and Spalding, though the latter is better known for bulb 

 growing ; opium-poppies are also grown. The sides of the Thames in 

 Essex and Kent are covered by rich alluvial soil, forming rich pastures 

 called marshes. At Cliffe, in Kent, there are good orchards on this 

 soil. At Sandwich there is similar soil on which fruit is grown ; here 

 also market gardening, which was first started by the refugees from the 

 Continent when religious persecution was rife, is carried on. There is 

 rich alluvial soil bordering the Severn between Bridgwater and Weston- 

 super-Mare, and extending many miles up the rivers Parret, Yeo, Axe, 

 and Brue. On the coast of Lancashire and the mouth of the Solway, 

 and far inland on the banks of mauy rivers, the soil is made more fertile 

 from alluvial deposits. Examples of such land are to be found on the 

 banks of the Ouse, Derwent, Trent, Wye, and Usk. 



Peat and Fen. — Peat accumulates quickly in stagnant water, filling 

 up hollows, and at last forming land safe for the foot to traverse ; such 

 is seen at Chat Moss, west of Liverpool, the moors of Yorkshire, and on 



