40 An Account of the Soil [pt. I 



ditions, hence the dark colour facilitates the warming 

 of the soil in spring. 



2. The organic matter greatly increases the capacity 

 of the soil for holding water. A soil rich in organic 

 matter is throughout the summer and autumn dis- 

 tinctly moister than a soil poor in organic matter 



(p. 181). 



3. Organic matter facilitates the production of a fine 

 tilth and a good seed bed, and it renders cultivation 

 more easy. 



Soils well supphed with organic matter are therefore 

 very valuable to the agriculturist both by reason of the 

 large amount of nitrogenous substances they contain 

 and also because of the ease with which they can be 

 worked. Examples occur in the fen districts in this 

 country, in the prairies of Western Canada, the black 

 earth or Tchernozem of Russia and elsewhere. Wherever 

 they occur these black soils are promptly taken up for 

 cultivation. 



There is, however, another type of organic matter 

 which is less widely distributed and much less useful. 

 Peat is organic matter but it is too acid and not suffi- 

 cientty decomposed to be of much value, hence peaty 

 soils are not in high agricultural repute. Intermediate 

 between peat and fen comes another type found in the 

 carr soils, which can be made distinctly useful by dress- 

 ings of lime. Owing to the great importance of the 

 organic matter chemists have made many attempts to 

 determine just how much is present in the soil. Advan- 

 tage is taken of the fact that organic matter bums away 

 while mineral matter does not: hence some of the soil 

 is burnt, and the loss of weight is measured (p. 227). 

 This method is simple, but unfortunately it is not quite 



