HISTORICAL AND INTRODUCTORY 



TABLE I. STATISTICS OF A ROTATION. BOUSSINGAULT (46). 



1000 kilograms per hectare = 16 cwt. per acre. 

 TABLE II. NITROGEN STATISTICS OF VARIOUS ROTATIONS. BOUSSINGAULT (46). 



leurs parties vertes sont aptes a le fixer ". Boussingault's work covers 

 the whole range of agriculture and deals with the composition of 

 crops at different stages of their growth, with soils and with problems 

 in animal nutrition. Some of his work was summarised by Dumas in 

 a very striking essay (87, see also 47) that has been curiously over- 

 looked by agricultural chemists. 



During this period (1830 to 1840) Carl Sprengel was studying the 

 ash constituents of plants, which he considered were probably essential 



1 Catch crop, i.e. taken in autumn after the wheat. 



2 This crop does not belong to the leguminosae, but it is possible that the nitrogen 

 came from the soil, and that impoverishment was going on, 



Z 



