xvn UTILISATION OF THE SOIL 209 



being interested in the subject, and following it 

 along many different lines. One point of great 

 importance caine out of researches which had only 

 an indirect reference t-o the nitrogen problem. This 

 was the gradual development of our knowledge of 



FIG. 45. Camels carrying Green Berseem, or Egyptian Glover, to 

 market in Egypt. The clover is grown both as a food for 

 animals and because it improves the soil. 



the minute organisms called bacteria, which were 

 shown to be the causes of many processes previously 

 regarded as mysterious. 



In 1876 the great French chemist Berthelot 

 pointed out the possibility that bacteria with the 

 power of fixing free nitrogen exist in normal soil. 

 This, as he showed, might explain some of the 

 differences between Boussingault's various experi- 



p 



