118 EXPERIMENT STATION RECORD. 



SOILS. 



Various studies on the arable soils of the Pas-de-Calais, A. 



Pagnoi^l {Tcrres Arables du Pas-de-Calais, Arras: 1894, pp. 138, Jig. 

 1, map 1). — This is an elaborate report on investigations of the soils of 

 the region of Pas-de-Calais commenced in 1886, and includes descrip- 

 tions of methods, tabulated chemical and mechanical analyses of 97 

 soils Avitli detailed descriptions of samples, accounts of investigations 

 on the humidity and absorptive power of soils and the changes which 

 salts undergo in the soil, and i>ractical conclusions deduced from the 

 investigations. 



Methods. — In sampling, a held was selected which was typical of one 

 of the classes of the soil of the territory examined and samples were 

 taken as a rule down to a depth of 20 or 30 cm. at 10 different points, 

 although care was taken not to go below the surface soil in .any case. 

 At the same time data relating to the agricultural value and adapta- 

 bility of the soil wei-e collected. 



For analysis, the air-dried soil was sifted through a sieve containing 

 lli meshes to the centimeter (less than one eighth mm. in diameter). 

 The residue left on the sieve was designated gravel, or coarse earth. 

 In order to separate this portion comi)letely the soil was shaken up 

 with water and washed through the sieve. 



The method used in the determination of the proportion of clay in 

 soils was as follows : 4 gm. of soil was introduced into a tube divided 

 into centimeters and millimeters, about 3.5 cm. long and 1 cm. in 

 diameter, a little lime water was added, and the whole shaken up 

 thoroughly. The lime water used for this purjjose should register 25° 

 by the liydrometer. The volume of liquid was then increased to 200 

 mm., shaken again for 2 minutes, and the tube allowed to lie in a slightly 

 inclined i)osition for minutes. The liquid was then found to have 

 cleared api)reciably at the top. The line of demarcation between the 

 turbid and the limpid i)arts was generally well deliued. The height of 

 the turbid portion (or "clay degree") Avas about 25 to 20 mm. with i^ure 

 sand, 45 to 00 with ordinary loam soils, 00 and above with very heavy 

 soils, and finally about 200 with very strong clays. 



For rapidly determining the carbonate of lime in the soil about 10 

 degrees of the soil was introduced into a special carbonic acid apparatus, 

 which is described and illustrated, and the number of bubbles of gas 

 evolved on the addition of nitric acid counted. By check observations 

 on i)ure carbonate of lime the Aveight of carbonic acid corresponding 

 to each bubble was determined and the results applied in the estimation 

 of carbonate in the soil. 



Humus was determined by extracting the soil with caustic soda solu- 

 tion and comparing the color of the extract thus obtained with a stand- 

 ard solution of caramel. By this method ordinary soils showed a 



