SOILS 



SOKOTO 



557 



Popularly speaking, the breaking down of rocks 

 by weathering results in the buuding up of soils, 

 and the composition of soils so formed must vary 

 in proportion to the kind and number of minerals 

 employed in the process. The principal minerals 

 so employed are felspar, quartz, mica, talc, lime- 

 stones (including^ chalks, marls, &c. ), hornblende 

 (amphibole, augite, olivine, &c. ), clays, and zeo- 

 lites. Soils formed from the rocks underlying them 

 are designated sedimentary, while transported 

 soils are those derived from rocks at higher levels : 

 thus, if carried down by glaciers they are termed 

 drift soils, if carried by running water they are 

 known as alluvial soils, and the combination of these 

 two agents results in co-alluvial soils. Anderson 

 classified soils according to ' their general physical 

 characters, and the ordinary mode followed in prac- 

 tice of dividing them into clays, loams, &c.' They 

 are also frequently classed thus : siliceous or sandy, 

 calcareous, argillaceous, and vegetable or peaty, 

 while a somewhat elaborate subdivision of these is 

 given in Schubler's classification. 



Generally speaking, a mixed soil will possess 

 important advantages over clay, chalk, or siliceous 

 soils, and this mixing is performed by nature her- 

 self, as. already described, where there is a dual 

 outcropping of rocks ; while the art of man effects 

 what is practically the same thing by claying, 

 liming, marling, &c. The chemical composition 

 and physical conditions of soils have until quite 

 recently been about the only features which received 

 consideration, but it is now beyond doubt that the 

 biological condition is of at least equal importance, 

 for, in regard to a well -drained soil, sterility and in- 

 fertility are synonymous terms. This new doctrine 

 solves at once the problems which for many genera- 

 tions have been insurmountable in such cases, 

 for instance, as two soils having the same chemical 

 composition, and one being fertile and the other 

 barren. Another highly important consideration 

 is that sterile soils are practically non-retentive; 

 and if that be so, all the hitherto obtaining doc- 

 trines which have ascribed to silicates, oxides, &c. 

 such unerring precision in forming new and definite 

 but purely chemical relationships with added sub- 

 stances, such as phosphates, potash and ammonia 

 salts, &c., must fall. It has been (and is still) 

 customary for exponents of agricultural science to 

 remark that it was a curious thing that the valu- 

 able nitrates were not retained by soils were 

 indeed easily washed out, and were more or less 

 always to be found in drainage waters, while phos- 

 phoric acid, potash, or ammonia was rarely if ever 

 so; but according to the germ theory there is 

 nothing curious about it, and it could not be other- 

 wise in a fertile soil. It is evident that many of the 

 heretofore established certainties of soil science and 

 of agriculture are destined to l>e overthrown. Capil- 

 larit.v, for instance, is doomed ; for fertility of soil is 

 incompatible with that condition, and it is scarcely 

 ''iiiipatihlf with drains operating at the lower end of 

 the capillary tubes. Drainage dogmas also require 

 modification, in so far, at least, as they declare 

 the removal of water which is surely antithetic 

 to capillarity and the opening up of a path for the 

 entrance of atmospheric air to be the chief functions 

 of drains. Plants can live in water, but not in an 

 atmosphere of carbon dioxide ; a fertile soil is as 

 prolific a source of this gas as the brewer's fer- 

 menting tun, and but for the presence of drains 

 Le. the removing per descensum of carbonic acid 

 no plant could grow. It is also maintained that 

 the entrance of carbon dioxide is essential because 

 of its function as a soil solvent ; but from what lias 

 been said it is evident there is something wrong with 

 the theories. Free entrance of oxygen to soils is 

 necessary for root life, and that is the reason why 

 removal of the over-abundant carbonic acid becomes 



imperative ; but it is not the case that it is neces- 

 sary to nitrification, and the leguminosoe can grow 

 robustly in what is practically an atmosphere of 

 carburetted hydrogen, so long as calcium carbonate 

 is maintained in the surface soil. Strange as this 

 may seem, it has been demonstrated on fields in 

 Midlothian ; and the fact goes to show that the 

 nitrifying organisms in soils can produce from 

 calcium carbonate all the oxygen required by them 

 for their life and work. This, indeed, is one of the 

 great functions of lime in soils. Lime cannot be 

 replaced by magnesia in soils, nor magnesia by 

 lime ; thus in fruit formation lime cannot per- 

 form the functions of magnesia, while lime in 

 addition to its all-importance as a salifiable base 

 becomes the great carrier of food-stuffs into the 

 plant, where again it is of paramount importance 

 as a fixer of the acid product of the oxalic fermenta- 

 tion, in which r61e magnesia is useless. 



An article on soil formation would be incom- 

 plete if reference were not made to the important 

 part played by earthworms (Lumbricus terrestris 

 especially; see EARTHWORMS); but while they 

 bring up much valuable material from the subsoil, 

 they are great robbers of lime from the surface soil. 



The views above stated are more fully treated in a 

 work on the subject by the present writer and Mr A. N. 

 M 'Alpine (1892). There are also works by Scott Burn, 

 Fream, Scott and Morton, Johnson, Munro and Wrightson, 

 Brannt, &c. See also A.GBICBLTUBE, MANURES, NITRI- 

 FICATION, &o. 



Soissons. a .town and fortress of France, dept. 

 Aisne, stands on the river Aisne, 65 miles NE. of 

 Paris by rail. Soissons is the key of Paris for an 

 army invading France from the Netherlands, and 

 is the meeting-point of several military roads. The 

 principal building is the cathedral, founded in the 

 12th century, the library of which contains many 

 rare MSS. There are also some remains of the 

 great castellated abbey of St Jean des Vignes 

 (1076), where Thomas a Becket found refuge 

 when in exile. The church of St Peter ( Roman- 

 esque) dates from the 12th century ; there are slight 

 remains of the once celebrated abbey of Notre 

 Dame (founded 660) and of the abbey church of St 

 Leger(1139). Quite near to Soissons is an insti- 

 tute for deaf and dumb, which occupies the site 

 of the famous abbey (560) of St Medard, where 

 Clothaire and Siegbert were buried. The civil 

 buildings embrace a college and a museum of an- 

 tiquities. Pop. 11,850, who carry on varied in- 

 dustries. Soissons is one of the oldest towns in 

 France, and was celebrated even in the time of the 

 Romans, when it bore the name first of Novio- 

 dunum, and afterwards of Attgiista Suessionum ; 

 hence its modern name of Soissons. It was the 

 second capital of Gallia Belgica, and subsequently 

 the most important town of the Romans in 

 northern Gaul. Near to it Clovis overthrew 

 Syagrius, the Roman commander, in 486. The 

 same prince made Soissons the seat of the Prankish 

 monarchy of Neustria. Here Pepin was crowned 

 king, and Louis the Pious imprisoned. It was the 

 gathering-place of more than one important council 

 and has been repeatedly captured and sacked in 

 war ^.g. six times during the Hundred Years' 

 War, by the Armagnac party in 1414, by Charles 

 V. (1544), the Huguenots (1565), three times in 

 1814, and by the Germans in 1870. 



Sokc, a form of the word Soe, meant in old 

 English times both the privilege of holding a court 

 and the district held by tenure of Socage (q.v.). 



Sokoto, a Central African state, bounded by 

 the Sahara, the Niger, the Benuwe and Bornu. 

 The mass of the population are Haussa (q.v.), but 

 ruled by Fulahs 'q.v.). Gando is dependent on 

 Sokoto, which itself is largely controlled by the 

 British Niger Company. 



