96. PKEPAEATION OF THE SAMPLE FOR ANALYSIS. 167 



ed by the plough, and is usually readily distinguished 

 from the upper soil by its physical characters, among 

 which a lighter color is prominent, owing to the absence 

 of humus. If this subsoil is to be examined, a sample 

 of it should be taken out in the same manner as directed 

 for the upper soil, to the depth of about 60 cm., and the 

 depth of the cavity noted. 



The sample is taken, according to the object of the 

 analysis, either 



«, from one or from several spots in the field, in order 

 to subject each sample to a separate analysis; or 



Z>, for an average representation of the soil of the whole 

 field ; in this case, several portions of earth are taken 

 from points distributed in a regular manner over the 

 field, all of which are most carefully mixed together, and 

 4-6 kilos, of the mixture, free from any large stones, are 

 preserved as the average sample. 



If the character of the soil varies materially in differ- 

 ent parts of the field, samples from several spots should 

 be analyzed separately. 



A small portion of the sample should be put at once in 

 a well-stoppered bottle ; the remainder may be allowed 

 to become air-dried^ by exposing it in a thin layer, in 

 summer, to the common temperature in the shade, or, in 

 winter, to that of a warm room, or a moderately warm 

 drying-chamber, heated to 30°-40° C. ; in either case it 

 should be carefully protected from dust. 



At the time of taking the sample of the soil, obser- 

 vations should be made in regard to the following points : 



a. The geognostic origin of the soil. 



h. The nature of the underlying strata, to the depth 

 of 1-2 metres, if practicable. 



c. The meteorology of the locality — ^l:>y consulting me- 

 teorological records, if possible; otherwise, by the general 

 opinion of the neighborhood; in this connection, the 



