615 



SODIUM-ETHYL. 



SOIL. 



Ml! 



some advantages over hydrate of potash, inasmuch as it IB not liable to 

 spread or run. 



It is only when in combination with carbonic acid that it is used to 

 correct acidity. It exists in three states, namely, carbonate, sesqui- 

 carbonate, and bi-carbonate : the causticity of these is less in propor- 

 tion to the increase of the acid. These preparations, administered in 

 various ways, but chiefly in solution, are much used to counteract real 

 or presumed acidity of the stomach. The abuse of the analogous 

 preparations of potash has been already pointed out. [POTASSIUM.] 

 The same caution is necessary as to soda-water, when that really con- 

 tains any carbonate or bi-carbonate of soda, as it not unfrequently 

 consists only of carbonic acid compressed into the water. The saline 

 draughts so commonly employed in the medical practice of this country 

 are liable to the same objection, and in all cases of debility, especially 

 in the phosphatic diathesis, do infinite harm. For an opposite reason, 

 they are extremely serviceable in all inflammatory complaints : the 

 period when they should be discontinued can only be determined by an 

 intelligent medical attendant. 



The preparations of soda possessed of purgative properties are the 

 sulphate, or Glauber's salts, the phosphate, and the triple salt, called 

 sodjc-potassio-tartras, or Rochelle salts, of which potash is also a con- 

 stituent. Of these it is only necessary to observe that of the sulphate 

 a much larger dose is required than of the corresponding salt of potash ; 

 and that the phosphate, being nearly tasteless, and extremely mild in 

 Hs action, in a very proper aperient for delicate persons. A nearly 

 similar character belongs to the Rochelle salt, but as this is decom- 

 posed in the stomach, it is as hurtful as the common saline draughts 

 in cases of debility, though very beneficial in inflammatory disorders, 

 particularly in both acute and chronic duodenitis. The same remark 

 is applicable to the so-called Seidlitz powders formed with Rochelle 

 salt and bi-carbonate of soda, to which, when dissolved, a solution of 

 tartaric acid is added, and the mixture drank in the state of effer- 

 vescence. The most quickly acting aperient is a Seidlitz powder 

 dissolved in warm water ; this is most proper at the commencement 

 of common colds, influenza, and inflammatory diseases, but it should 

 not be repeated without medical sanction, especially in influenza, where 

 extreme debility speedily ensues. 



The preparations of soda possessed of diuretic properties are the 

 bi-borate and the acetate. The former of these has been already 

 treated of [BORAX], and the second is rarely used, though, from not 

 deliquescing, it has the advantage over acetate of potash, that it can 

 be administered in the form of powder. 



Chloride of sodium possesses purgative and emetic properties, which 

 render it useful as a domestic remedy. Its other uses have been 

 already pointed out. [BATHISO; AXTHELMINTICS; FOOD.] Along 

 with lemon juice it is a great means of checking sea-sickness. 



Chloride or hypochlorite of soda is a powerful disinfecting agent. 

 [ANTISEPTICS.] It is of great utility in the malignant sore throat of 

 scarlatina, and in diphtheria. 



Bisulphite of soda is a powerful antiseptic. It effectually checks or 

 prevents fermentation. (Macculloch ' On Wine Making.') It retards 

 the decomposition of animal substances, and for that purpose is used 

 in Parisian dissecting-rooms. 



Hypophosphite of soda is sometimes of use in the early stages of 

 consumption ; also in anaemia and chlorosis. 



Valerianate of soda is a useful anti-spasmodic in some forms of indi- 

 gestion, with spasms from unhealthy acids in the stomach. 



SODIUM-ETHYL. [OKOANOMETAI.I.IC BODIES.] 



SOFTNESS is a condition of solid bodies in which the particles are 

 held together by a cohesive power of small intensity : in consequence 

 of this, such bodies change their figures upon the application of a small 

 degree of force ; and they do not recover their previous forms upon its 

 removal. 



This condition is the opposite of hardness, in which the particles 

 are held together by a power of cohesion so great that they cannot 

 be separated by any force which it may be convenient to apply to 

 them. No body in nature is known to possess either of these qualities 

 absolutely ; but in contemplating the mechanical actions of soft bodies, 

 balls of wet clay are generally used, while blocks of wood acting 

 against one another in the directions of their fibres are frequently used 

 to illustrate the effects of hardness. Balls of glass or ivory, or steel 

 springs, serve to show the mechanical actions of elastic bodies. 

 [COLLISION on PERCUSSION OF BODIES.] 



>i 1 1 1,. Wherever the surface of the earth is not covered with water, 

 or is not naked rock, there is a layer of earth, more or less mixed with 

 uains of animal and vegetable substances, in a state of decom- 

 position, which is commonly called the 



The nature and composition of the soil, and consequently its greater 

 or less aptitude to the growth and maturity of vegetable productions, 

 depend on the composition, the proportion and the mechanical 

 structure of the various substances of which it consists. When the 

 soil is favourable- to the chemical action by which the elements are 

 combined to form vegetable substances, and admits that quantity of 

 air and moisture without which this chemical action cannot take place 

 in any given climate or temperature, vegetation goes on rapidly, and 

 all the plants which are suited to the climate grow in the greatest 

 perfection, and bear abundant fruits. 



It is not however very frequently the case that a soil posuesses all 



those qualities on which great fertility depends. So many circum- 

 stances must concur to make a soil highly fertile, that the great 

 majority of soils can only be made to produce abundantly by being 

 improved by art both in their texture and composition. Hence the 

 practice and science of agriculture, which is founded on experience, 

 but to which every progress in science also affords great assistance, by 

 the additional light which every new discovery throws on the true 

 theory of vegetation. 



There are various modes of distinguishing soils, without entering 

 into a minute analysis of their component parts. The simplest and 

 most natural is to compare their texture, the size and form of the 

 visible particles of which they are composed, and to trace the probable 

 source of their original formation from the minerals which are found 

 around or below them, or the rocks from which they may have been 

 slowly separated by the action of the elements. The science of 

 geology, which teaches the relative position and nature of the minerals 

 of which the outer crust of the earth is formed, is consequently of the 

 greatest utility in aiding us to compare different soils and in ascertain- 

 ing their composition. 



The knowledge which geology imparts is however not sufficient for 

 the minuter classification of soils ; for it is found by experience that 

 the soils which lie over or near the different strata, as they appear 

 near the surface, vary greatly, although they retain some general 

 character which distinguishes them from others. The streams which 

 descend from the hills, and flow towards the valleys, and through 

 them to the sea, carry to a great distance the minuter portions of the 

 minerals which they flow over in their course, while the larger and 

 heavier are deposited much sooner. Hence the heterogeneous mixture 

 of various earths and stones, and their stratification in thin layers, as is 

 often found when a soil is examined which has never been disturbed 

 by cultivation. 



It is not sufficient to class sous according to the substance which 

 predominates, as has been usually done, such as sandy, gravelly, 

 chalky, or clay soils ; for this gives very imperfect information 

 respecting their nature or fertility ; neither is it altogether sufficient 

 to class them according to any particular geological formation. 



The soils which have been evidently formed from the rocks which 

 are supposed to be of secondary formation are fertile according to the 

 proportion of the earths of these rocks which they contain. 



Argillaceous earth exists in some proportion in almost every rock. 

 It has the property, when mixed with other substances, as silica or 

 lime, of fusing into a stone of great hardness and insolubility. In 

 this state its effect on the soil is not to be distinguished from that of 

 silica; and by burning common clay, or clay mixed with carbonate of 

 lime, a sandy substance is produced resembling burnt brick, which 

 tends greatly to improve the texture of those clays which contain 

 little or no sand in their composition. It must be remembered that 

 the stiffest clays contain a large portion of silica in an impalpable 

 state ; but this, instead of correcting their impermeable and plastic 

 nature, rather adds to it. It is only palpable sand which with clay 

 forms what is commonly called loam, and which, when the sand is in 

 due proportion with a mixture of organic matter, forms the richest 

 and most easily cultivated soils. Some of the rocks of secondary 

 formations contain a considerable portion of alumina and lime ; and 

 when these earths meet with crystallised sand, a compound, or 

 rather a mixture is formed, which has all the requisite qualities, as to 

 texture, to produce the most fertile loams. The only deficiency is 

 that of organic matter ; but this is so readily accumulated wherever 

 vegetation is established, or can be so easily added artificially, that 

 these loams may always be looked upon as the most favourable soils 

 for the usual agricultural operations ; and if a considerable depth of 

 loam is found, which neither retains water too long nor allows it to 

 percolate too rapidly, it may be looked upon as a soil eminently capable 

 of the highest degree of cultivation, and on which no judicious outlay 

 of labour will ever cause loss or disappointment to the farmer. 



Thus, the greensand which lies under the chalk, and appears near the 

 surface in several parts of Britain, consists of silicious, argillaceous, 

 and calcareous earth, intimately combined and in a high state of 

 subdivision, and yet not forming a compact paste with water so as to 

 dry in hard lumps, but having rather the loose appearance and granula- 

 tion of fine sand, whence its name. On this soil are found the finest 

 wheats ; but such is the variety of ita form as it approaches towards 

 the chalk or crystallised sand, or the plastic clay, that the soils which 

 it forms have every degree of texture, from loose sands to stiff marls, 

 whose chief use is to mix with other soils and improve them. In 

 general however it may be said that the soils of which the greensand 

 forms a considerable part are productive and easily cultivated, and that 

 they repay the labour and manure expended on them better than urn. t 

 others. A narrow strip of this sand crosses Bedfordshire, and in the 

 neighbourhood of Sandy and Biggleswade are raised some of the finest 

 culinary vegetables which come to the London market. This sand, 

 though light in appearance, and very easily worked, contains much of 

 the impalpable substance mentioned before ; and this, with careful 

 cultivation and manuring, makes it peculiarly suited for gardens as 

 well as for corn-fields. In its natural state it is easily distinguished 

 from other sands by certain dark particles in it, which give it the 

 greenish hue from whence it has been called greensand, and also by its 

 effervescence with strong vinegar or any other acid. 



