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During the diffraction of these X rays by the atoms arranged regularly in 
the parallel plans of distance d, the mutual reinforcement of the reflected 
rays is produced under the following conditions: 
2 d sin($) = m d Relation of WOULF-BRAGG ( 1 ) 
m : integer , 8 : complementary angle of incidence angle 
The X rays diffraction allows us to study and to caraterize a structure 
of crystals which will be identified thanks to established abacuses of 
crystalline and mineral elements. 
figure 3 
Therefore, we have been interested to the soil composition study and we 
propose to make the rocks and the soils mineralogie constitution determination 
by one diffractometric to X rays (Cobalt anticathod) and by the soil spectral 
caracteristic study belonging to a test site called OUM DELOUA ar the east of 
Laghouat (Algeria). This sire is caracterized by a sandy cover presenting a 
more or less continued variation of the mineralogie composition , and whose 
the differences have been perfectely identified on the studied ground. The 
figure 4 and the image 3 present a segment test site (500x500 m) with the 
legend. 
Image 3