purposes, the finer the particles which compose a soil, within limits, castcri* 

 paribus, the better the soil will be for general agricultural purposes. Hence 

 although, as above remarked, a- complete mechanical analysis was not, as a 

 rule, included in these investigations, a partial sifting out of the soil has 

 invariably preceded the chemical analysis proper, so that any plant food 

 material that may have been locked up within the coarser soil particles has 

 been left out of account in reckoning up the proportion of "available" 

 plant food present in the soil. 



In preparing a soil for the chemical analysis, the " field sample " is 

 first of all freed from pebbles by dry-sifting a sufficient quantity through 

 a brass-bottomed sieve with circular perforations 3 mm. in diameter. All 

 that passes through this sieve is denominated " true soil/' 250 grammes of 

 this "true soil " are placed in a porcelain dish; about half a litre of dis- 

 tilled water is poured on, and the dish is allowed to digest on a water bath 

 for at least two hours, the contents being stirred at frequent intervals. 

 When the soil has thus been sufficiently softened, it is sifted in the follow- 

 ing manner : A special sieve (Kahl's " Messingdrahtsieb " No. 50), having 

 meshes of diagonal measurement *45 to '50 mm. and '35 to '39 laterally, is 

 held over a dish containing distilled water; the moistened soil is placed in 

 the sieve, and the latter is then immersed with the bottom about an inch 

 or more below the water level in the dish. By the aid of a small brush the 

 soil is now stirred until particles no longer pass through, after which the 

 residue in the sieve is thoroughly washed with distilled water. The ma- 

 terial which passes through the sieve is dried, together with the wash-water,, 

 on a water bath, and the weight is then recorded in percentage of the* 

 "field sample." The residue thus obtained by evaporation of the sifted 

 soil and water is called " fine earth," and is subsequently utilised, accord- 

 ing to the standard method of chemical analysis adopted, for the determina- 

 tion of lime, potash, and phosphoric oxide. 



Another sufficient portion of the " field sample " is dry-sifted through 

 a brass-bottomed sieve with circular perforations 1 mm. in diameter. That 

 which passes through is termed "earth," and is employed in determining 

 the amounts of moisture, organic matter, chlorine, and nitrogen. 



The chemical analysis proper has now to be considered. As already 

 indicated, the proportions, of soil-constituents mentioned in all the subse- 

 quent tables of analysis by the standard method are calculated and stated 

 in terms as below : 



" Moisture " ] 



" Organic matter " ( . 



" Chlorine " ( m P ercenta S e of earth." 



" Nitrogen " ) 



44 Lime " ) 



" Potash " V in percentage of " fine earth." 



44 Phosphoric oxide" ) 



" Fine earth " in percentage of " field sample." 



Details are appended of the methods followed in determining these 

 constituents. Two separate portions of soil are used, prepared as already 

 described (the " earth " by sifting through a 1 mm. sieve, the " fine earth " 

 by sifting through what is practically a \ mm. sieve) ; these are, after 

 treatment, allowed to become air-dry and bottled. 



Moisture. Ten grammes of " earth " are weighed in a tared platinum 

 crucible, heated in an air bath from three to four hours, at a temperature 

 from 105 C. to 110 C., allowed to cool in a desiccator, and rapidly 

 weighed again. 



Organic and volatile matter. The crucible containing the perfectly dry 

 soil used in the determination of moisture is heated to redness until all 

 organic matter has been burnt away. It is then cooled in a desiccator and 



